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NCERT Solutions for Class 10 Science Chapter 8 How do Organisms Reproduce

These Solutions are part of NCERT Solutions for Class 10 Science. Here we have given NCERT Solutions for Class 10 Science Chapter 8 How do Organisms Reproduce. Learn Insta provides you the Free PDF download of NCERT Solutions for Class 10 Science (Biology) Chapter 8 – How do Organisms Reproduce? solved by Expert Teachers as per NCERT (CBSE) Book guidelines. All Chapter 8 – How do Organisms Reproduce? Exercise Questions with Solutions to help you to revise complete Syllabus and Score More marks.

NCERT Questions

In Text Questions

Question 1.
What is the importance of DNA copying in reproduction ? (CCE 2011, 2015)
Answer:
DNA carries hereditary information not only for controlling cellular functions but also all the structural and functional traits of organism. It is because of the latter that single celled zygote is able to form the whole multicellular organism. During reproduction there is formation of new cells which must carry the same amount and type of hereditary information as present in the parent cell. This is accomplished by DNA copying, which occurs prior to each cell division. DNA copying is not error proof. Errors give rise to variations.

More Resources

• NCERT Solutions for Class 10 Science
• NCERT Exemplar Solutions for Class 10 Science
• HOTS Questions for Class 10 Science
• Value Based Questions in Science for Class 10
• Previous Year Question Papers for CBSE Class 10 Science

Question 2.
Why are variations beneficial to the species but not necessarily for the individual ? (CCE 2011, 2012)
Answer:
Many of the variations are pre-adaptations which have no immediate benefit to the individuals. However, they remain in the population. Whenever, environment undergoes a drastic change, the pre-adaptations present in some members of the population allow the latter to survive, grow and regain its former size. Therefore, it is not necessary that variations are beneficial to individuals developing them but can prove useful to the species.

Question 3.
How does binary fission differ from multiple fission ?
Answer:

Question 4.
How will an organism be benefited if it reproduces through spores ? (CCE 2011, 2012)
Answer:
Sporulation or spore formation is a method of asexual reproduction where each individual produces a number of spores. On germination each spore forms a new individual, e.g., Rhizopus.

1. All the daughters formed through spores are genetically similar.
2. Spores are a means of dispersal. They help in spreading the organism far and wide.
3. Spores can also function as a means of perennation or passage through unfavourable conditions.

Question 5.
Can you think of reasons why more complex organism cannot give rise to new individuals through regeneration.
Answer:
Regeneration is the ability of an organism to replace lost or injured parts so as to form the whole individual from an incomplete form or fragment by remodelling and growth of somatic cells through dedifferentiation, division, morphogenesis and redifferentiation. The ability for regenerative multiplication is present in simpler organisms because most of their cells can undergo dedifferentiation. However, it is limited to certain cells in complex organisms.

1. The stem cells of complex organisms can form lost tissues and organs but not the complete individual as the highly differentiated tissues and organs do not allow this.
2. In complex organisms regeneration is under neurohormonal control. Fragments do not have nervous or hormonal stimulus to grow into complete organisms.

Question 6.
Why is vegetative propagation practised for growing some types of organisms ?
Answer:
Vegetative propagation is practised in a number of horticulturally and economically important plants because it is advantageous.
Advantages:

1. Seedless Plants. Vegetative propagation is the only known method of multiplication of seedless plants, g., Banana, Sugarcane, Pineapple, Jasmine, some varieties of Orange, Rose.
2. Uniform Yield. Seeds and fruits are of uniform quality, size, taste and aroma.
3. Genetic Uniformity. Vegetative propagation gives a genetically uniform population.
4. Good Qualities. Good qualities of a variety can be maintained indefinitely.
5. Survival Rate. Survival rate of the daughters is nearly 100% while in case of seed grown plants, it is 10%.
6. Quicker Method. Vegetatively reproduced plants bear flowers and fruits earlier than the plants raised through seeds. Potato requires only three months for forming a new crop if raised from tubers. It takes 15 months if raised from seeds.
7. Introduction in New Areas. In areas where seed germination fails to form mature plants, vegetative reproduction can help in establishing the plants.

Question 7.
Why is DNA copying an essential part of the process of reproduction ?
Answer:
Cell multiplication is essential for reproduction either as a means of multiplication in unicellular organisms or as a means of development of multicellular body from a single celled zygote. Cell multiplication cannot occur without DNA replication or DNA copying because each new cell must carry the full DNA complement.

Question 8.
How is the process of pollination different from fertilization ?
Answer:

Question 9.
What is the role of seminal vesicles and the prostate gland ? (CGE 2011, 2012)
Answer:
Seminal Vesicles: They secrete 60-70% of semen plasma that is alkaline and viscous having fructose (for nourishing the sperms), fibrinogen, proteins and prostaglandins. Prostaglandins cause movements in the genital tract of the female. Sperms are also activated by secretion of seminal vesicles.
Prostate Gland: It produces 20-30% of semen plasma. The secretion is alkaline and viscous. It has clotting enzyme and chemical essential for sperm activity.

Question 10.
What are the changes seen in girls at the time of puberty ?
Answer:

1. Breast size begins to increase. There is darkening of skin of nipples below the tips of breasts.
2. Menarche or beginning of menstruation.
3. Broadening of pelvis,
4. Deposition of fat in face, buttocks and thighs,
5. Increased vasculature of skin and hence increased warmth of skin,
6. Rounding of body ccthtours.
7. High pitched voice,
8. Slow growth of ovaries, fallopian tubes, uterus, vagina, enlargement of labia, etc.

Question 11.
How does the embryo get nourishment inside the mother’s body ? (CCE 2012)
Answer:
Embryo gets nourishment from mother’s body with the help of placenta through a cord called umbilical cord. Placenta contains many finger-like villi from the chorion covering of the embryo. They occur in contact with blood sinuses of the mother present in the endometrial lining of uterus. All nutrients (glucose, amino acids, vitamins, etc.) diffuse from mother’s blood into villi and from there to embryo through the umbilical cord.

Question 12.
If a woman is using a copper-T, will it help in protecting her from sexually transmitted diseases ?
Answer:
No, sexually transmitted diseases occur due to fluid to fluid contact that takes place in the vagina.

NCERT Chapter End Exercises

Question 1.
Asexual reproduction takes place through budding in
(A) Amoeba
(B) Yeast
(C) Plasmodium
(D) Leishmania.
Answer:
(B).

Question 2.
Which of the following is not a part of the female reproductive system in human beings.
(A) Ovary
(B) Uterus
(C) Vas deferens
(D) Fallopian tube.
Answer:
(C).

Question 3.
The anther contains
(A) Sepals
(B) Ovules
(C) Carpel
(D) Pollen grains.
Answer:
(D).

Question 4.
What are the advantages of sexual reproduction over asexual reproduction ?
Answer:
Asexual reproduction is monoparental, with no gametes, no meiosis and very little variations. Sexual reproduction is generally biparental involving fusion of gametes, meiosis and lot of variations.

Question 5.
What are the functions performed by testis in human beings ? (CCE 2011)
Answer:

1. Formation of sperms from germinal cells found in seminiferous tubules.
2. Secretion of hormone testosterone by Leydig cells. Testosterone induces secondary sexual characters at puberty. It helps in maintenance and functioning of secondary sex organs.

Question 6.
Why does menstruation occur ?
Answer:
Menstruation occurs in response to low level of estrogen and progesterone hormones which causes constriction of blood vessels in uterine wall, stoppage of nourishment to overgrown endometrium that sloughs off, passing out broken mucosal membrane, blood and mucus.

Question 7.
Draw a labelled diagram of L.S. flower.
Answer:

Question 8.
What are the different methods of contraception ?
Answer:

1. Mechanical Barriers like condoms, cervical cap, diaphragm.
2. Oral Contraceptives or oral pills like Mala D, Saheli
3. Intrauterine Contraceptive Devices (IUCD) like loop, bow, Cu-T.
4. Surgical Methods like vasectomy in males and tubectomy in females.

Question 9.
How are the modes for reproduction different in unicellular and multicellular organisms ?
Answer:

Question 10.
How does reproduction help in providing stability to population of species ?
Answer:

1. Replication of DNA.
2. Growth and differentiation of cellular machinery.
3. Cell division. It is mode of reproduction in single celled organisms,
4. Development of special reproductive structures and formation of new individuals.
5. Continued replication of DNA, growth and cell division, formation of tissues, organs, etc. and maturation into a multicellular organism.

Question 11.
What could be the reasons for adopting contraceptive methods ?
Answer:

1. Enjoying a good reproductive health.
2. Protecting from sexually transmitted diseases.
3. Restricting the number of children.
4. Spacing the birth of children so as to properly look after them, provide them proper education without depleting the resources of the family.
5. Controlling population.

Selection Type Questions

Alternate Response Type Questions
(True/False (T/F), Right(√)/Wrong (x), Yes/No)

Question 1.
Basic event in reproduction is creation of DNA copy.
Question 2.
Plasmodium multiplies by binary fission.
Question 3.
Bryophyllum propagates through spore formation.
Question 4.
Copper-T is a contraceptive device used by women.
Question 5.
Hibiscus has unisexual flowers.
Question 6.
At the time of birth a girl baby has thousands of immature eggs.
Question 7.
Ovulation occurs in reproductively active females roughly in the middle of menstrual cycle.
Question 8.
Sperms mature at a temperature higher than that of human body.

Matching Type Questions

Question 9.
Match the articles given in columns A and B (single matching)

Question 10.
Match the contents of columns I, II and III (double matching) :

Question 11.
List the type of reproduction (A-asexual, V-vegetative, S-sexual) in the following organisms (Key or check list items)

Question 12.
Match each stimulus with appropriate response :

Fill In the Blanks

Question 13. ………………….. help in survival of the species in changing environment.
Question 14. ………………….. is common method of multiplication of Yeast and Hydra.
Question 15. Reproductive tissues begin to …………………….. when rate of general body growth begins to ………………… .
Question 16. Fallopian tubes are cut and ligated in ………………… .
Question 17. Bartholin’s glands are components of ……………………. reproductive system.

Answers:

NCERT Solutions for Class 10 Science Chapter 8 – How do Organisms Reproduce?

Hope given NCERT Solutions for Class 10 Science Chapter 8 are helpful to complete your science homework.

If you have any doubts, please comment below. Learn Insta try to provide online science tutoring for you.

In this chapter, students will come to know about early attempts at the classification of elements, Newlands Law Of Octaves, Mendeleev’s Periodic Table, the modern periodic table, metallic and non-metallic properties. At the end students are supposed to attempt question and answer exercise, multiple choice questions and group activity.

These Solutions are part of NCERT Solutions for Class 10 Science. Here we have given NCERT Solutions for Class 10 Science Chapter 5 Periodic Classification of Elements. Learn Insta provides you the Free PDF download of NCERT Solutions for Class 10 Science (Chemistry) Chapter 5 – Periodic Classification of Elements solved by Expert Teachers as per NCERT (CBSE) Book guidelines. All Chapter 5 – Periodic Classification of Elements Exercise Questions with Solutions to help you to revise complete Syllabus and Score More marks.

NCERT Solutions for Class 10 Science Chapter 5 Periodic Classification of Elements

Periodic Classification of Elements Class 10 Science In Text Book Questions

Question 1.
Did Doberiener’s triads also exist in the columns of Newlands’ octaves ? Compare and find out.
Answer:
Yes, some of the Doberiener’s triads did exist in the columns of Newlands’ octaves. For example,

More Resources

• NCERT Solutions for Class 10 Science
• NCERT Exemplar Solutions for Class 10 Science
• HOTS Questions for Class 10 Science
• Value Based Questions in Science for Class 10
• Previous Year Question Papers for CBSE Class 10 Science

Question 2.
What were the limitations of Doberiener’s triads ?
Answer:
Doberiener was in a position to identify three triads. It could not apply to all the elements known at that time. Therefore, the classification was not so useful.

Question 3.
What were the limitations of Nawlands’ Law of Octaves ?
Answer:

1. Actually this classification was successful only upto the element calcium. After that, every eighth element did not possess the same properties as by the element lying above it in the same group. For example, the elements cobalt (Co) and nickel (Ni) placed below chlorine had different properties. Same was the case with copper (Cu) placed after potassium in the same group.
2. Newland committed another mistake. He placed two elements in the same slot in a particular group. For example, Co and Ni in the first group after chlorine. Similarly, elements cerium (Ce) and lanthanum (La) were placed after yitterium (Y) in the same group. Newland could not offer any explanation for such an arrangement.
3. Newland somehow thought that only 56 elements existed in nature and no more elements were likely to be discovered. But this belief ultimately proved to be wrong.
4. When noble gas elements were discovered at a later stage, their inclusion in the table disturbed the entire arrangement.

Question 4.
Use Mendeleev’s periodic table to predict the formulae for the oxides of the elements : K, C, Al, Si, Ba.
Answer:
Oxygen is a member of group VTA in Mendeleev’s periodic table. Its valency is 2. Similarly, the valencies of all the elements listed can be predicted from their respective groups. This can help in writing the formulae of their oxides.

1. Potassium (K) is a member of group IA. Its valency is 1. Therefore, the formula of its oxide is K₂O.
2. Carbon (C) is a member of group IVA. Its valency is 4. Therefore, the formula of its oxide is C₂O₄ or CO₂.
3. Aluminium (Al) belongs to groups IIIA and its valency is 3. The formula of the oxide of the element is Al₂O₃.
4. Silicon (Si) is present in group IVA after carbon. Its valency is also 4. The formula of its oxide is Si₂O₄ or SiO₂
5. Barium (Ba) belongs to group IIA and the valency of the element is 2. The formula of the oxide of the element is Ba₂O₂ or BaO.

Question 5.
Besides gallium which two other elements have since been discovered that fill the gaps left by Mendeleev in creating his periodic table ?
Answer:
Two other elements are scandium (Sc) and germanium (Ge). In their gaps, the elements with names Eka-boron and Eka-silicon were placed.

Question 6.
What was the criteria used by Mendeleev in creating his periodic table ?
Answer:
Mendeleev used atomic masses of the elements as the criteria for creating his periodic table. In this table, the elements were arranged in order of increasing atomic masses.

Question 7.
Why do you think that the noble gases should be placed in a separate group ?
Answer:
In the Mendeleev’s periodic table, the elements have been arranged in the different groups on the basis of valency. For example, the elements placed in group I (IA and IB) have Valency equal to one. Same is the
case with the elements placed in other groups. Since the noble gas elements He, Ne, Ar, Kr, Xe, and Rn have zero valency, they could not find a place in Mendeleev’s periodic table. These have been placed in a separate group called zero group in the periodic table. Please note that the noble gas elements were not a part of the Mendeleev’s periodic table. They were added later on.

Question 8.
How could the Modern Periodic table remove various anomalies of Mendeleev’s periodic table ?
Answer:
We have already studied that the Mendeleev’s periodic table is based on the atomic masses of the elements whereas Modern Periodic Table takes into account their atomic numbers. Since the properties of the elements are linked with the electronic configuration of their atoms (i.e., atomic number), this means that Modern Periodic Table is better than the Mendeleev’s Periodic Table. The important advantages are listed.

1. The position of the elements in the periodic table are linked with their electronic configuration.
2. Each group is an independent group and the idea of sub-groups has been discarded.
3. One position for all the isotopes of an element is justified since the isotopes have the same atomic number. For example, the three isotopes of the element hydrogen e., protium, deuterium and tritium have atomic number one (Z = 1). Similarly, two isotopes of chlorine i.e. Cl-35 and Cl-37 are placed in the same slot since they have same atomic number (Z = 17).
4. The positions of certain elements which were earlier misfits in the Mendeleev’s periodic table  are now justified because it is based on   atomic numbers of the elements.  For example, Ar precedes K because its atomic number (18) is less than that of K (19).
5. It is quite easy to remember and reproduce.

Question 9.
Name two elements you would expect to show chemical reactions similar to magnesium. What is the basis for your choice ?
Answer:
Magnesium (Mg) belongs to group 2 known as Alkaline Earth Family. The two other elements belonging to the same group are calcium (Ca) and strontium (Sr). The basis of choice is the electronic distribution in the valence shell of these elements. All of them have two electrons each.

Question 10.
Name :
(a) three elements that have a single electron in their outermost shells.
(b) three elements that have two electrons in their outermost shells.
(c) three elements with filled outermost shells.
Answer:
(a) Lithium, sodium, potassium (Alkali metals present in group 1)
(b) Beryllium, magnesium, calcium (Alkaline earth metals present in group 2)
(c) Helium, neon, argon (Noble gases present in group 18).

Question 11.
(a) Lithium, sodium, potassium are all metals that react with water to liberate hydrogen gas. Is there any similarity in the atoms of these elements ?
(b) Helium is an unreactive gas and neon is a gas of extremely low reactivity. What, if anything, do their atoms have in common ?
Answer:
(a) The atoms of all these elements have one electron each in their valence shell. That is why, these elements are placed in the group 1 known as alkali metal group. The electronic configurations of these elements are given :

All the three elements evolve hydrogen gas on reacting with water
2 Li + 2 H₂O ———-> 2 LiOH + H₂
2 Na + 2 H₂O ————> 2 NaOH+ H₂
2 K + 2 H₂O ————> 2 KOH + H₂
Apart from this, all the elements happen to be the first elements of their respective periods. For example,

• Second period starts from lithium (Li)
• Third period starts from sodium (Na)
• Fourth period starts from potassium (K).

(b) Both these elements have completely filled shells. Helium (Z = 2) has two electrons in the only shell (K shell). The other element neon (Z = 10) has both K and L shells fully filled (2, 8). Because of the filled shells, the atoms of these elements do not have any desire to take part in chemical combination and they have been placed together in the same group known as group 18 or zero group.

Question 12.
In the modern periodic table, which are the metals among the first ten elements ?
Answer:
Metals among the first ten elements are lithium (Li) and beryllium (Be) . These are placed towards the left of the table.

Question 13.
By considering their position in the periodic table, which one of the following elements would you expect to have maximum metallic characteristics ?
Answer:
Before identifying the metallic character from the list of the elements, we must remember two points :

• The metallic character of an element is related to the electron releasing tendency of its atoms. Greater the tendency, more will be the metallic character.
• In general, metallic character of the elements increases down the group and decreases along a period.
  With the help of the Modern Periodic Table, let us identify the group and period to which these elements

Since the metallic character increases down a group and decreases along a period, the obvious choice is between two elements. These are Be (beryllium) present in group 2 and Ga (gallium) present in group 13. Now, the size of Ga is very big as compared to that of Be. Actually, the element Ga has three shells since it belongs to period 4 while the element Be has only two shells as it is a member of period 2. This means that the element Ge has a greater electron releasing tendency of its atom as compared to the element Be. Therefore, Ge has more metallic character, rather maximum metallic character among the elements that are listed.

Periodic Classification of Elements Class 10 Science NCERT End Exercise

Question 1.
Which of the following statements is not correct about the trends while going from left to right across the periodic table ?
(a) The elements become less metallic in nature
(b) The number of valence electrons increases.
(c) The atoms lose their electrons more easily.
(d) The oxides become more acidic.
Answer:
(c). The atoms lose their valence electrons with difficulty and not easily. This is on account of the reason that

• nuclear charge increases from left to the right since the atomic number of the elements gradually increases.
• with the increase in nuclear charge, the force binding the electrons with the nucleus increases. Therefore, the atoms lose their valence electrons with difficulty.

Question 2.
Element X forms a chloride with the formula XCI2 which is a solid with high melting point. X would most likely to be in the same group of the periodic table as :
(a) Na
(b) Mg
(c) Al
(d) Si.
Answer:
(b). The formula of the chloride of the element is XCl₂. This means that the valency of the element X is 2 since chlorine is monovalent. The element with valency 2 is expected to be present in group 2 to which magnesium (Mg) belongs.

Question 3.
Which element has :
(a) two shells, both of which are completely filled with electrons ?
(b) the electronic configuration 2, 8, 2 ?
(c) a total of three shells with four electrons in the valence shell ?
(d) a total of two shells with three electrons in the valence shell ?
(e) twice as many electrons in the second shell as in the first shell ?
Answer:
(a) The elements with completely filled shells are noble gas elements and they belong to group 18. Since the element has two shells ; it must be present in second period and is neon (Ne) with electronic configuration 2, 8.
(b) The electronic configuration suggests that the element belongs to third period and second group. It is therefore, magnesium (Mg).
(c) The element with three shells is present in third- period. Since it* has four electrons in the valence
shell, it must belong to group 14 and is silicon (Si) with electronic configuration 2, 8, 4.
(d) The element with two shells is expected to be present in the second period. With three electrons in
the valence shell, it must belong to group 13 and is boron (B) with electronic configuration 2, 3.
(e) The element has only two shells. The first shell can have a maximum of two electrons. The second shell has four electrons which is twice the number of electrons present in the first shell. Therefore, the electronic configuration of element is 2, 4. It is carbon with atomic number (Z) equal to 6.

Question 4.
(a) Which property do all elements in the same column of the periodic table as boron have in common ?
(b) Which property do all elements in the same column of the periodic table as fluorine have in common ?
Answer:
(a) The element boron (B) is the first member of group (also called column) 13. It has three electrons in
the valence shell (2, 3). The other elements included in the same column are aluminium (Al),
gallium (Ga), indium (In) and thalium (Tl). They too have three electrons in the valence shell of their atoms. Just like boron, these elements also show a valency of 3 in their compounds.
(b) The element fluorine (F) is the first member of group (also called column) 17. It has seven electrons in the valence shell (2, 7). The other members present in the same group known as halogen family are chlorine (Cl), bromine (Br), iodine (I) and astatine (At). They have also seven electrons in the valence shell of their atoms. Like fluorine, they all show a valency of 1 in their compounds.

Question 5.
An atom has electronic configuration 2, 8, 7.
(a) What is the atomic number of this element ?
(b) To which of the following elements would it be chemically similar ? (Atomic numbers are given in parentheses).
N(7), F(9), P(15), Ar(18).
Answer:
(a) The atomic number of the element is 17 (2 + 8 + 7 = 17).
(b) It would be chemically similar with fluorine (F) which has also 7 electrons in valence shell (2, 7)

Question 6.
The position of three elements A, B and C in the periodic table are shown below :

(a) State whether A is metal or non-metal.
(b) State whether C is more reactive or less reactive than A.
(c) Will C be larger or smaller in size than B ?
(d) Which type of ion, cation or anion will be formed by the element A ?
Answer:
(a) Group 17 represents halogen family. All the elements included in the family are Therefore, element A is a non-metal.
(b) Reactivity of non-metals is generally due to the electron accepting tendency of their atoms. Down the group, the atomic size increases. Therefore, the attraction of the nucleus for the outside electrons decreases. This means that down the group of non-metals, reactivity decreases. Thus, the element C is less reactive than the element A.
(c) Atomic size of the elements decreases along a period. The elements B and C are present in the same period. Since C is placed after B, the size of the element C is less than that of B.
(d) The elements A, as pointed out earlier is a non-metal which belongs to group 17. It has seven valence electrons (2, 8, 7). In order to have the configuration of the nearest noble gas element, it will take up one electron and change to anion i.e., A^– ion.

Question 7.
Nitrogen (atomic number 7) and phosphorus (atomic number 15) belong to group 15 of the periodic table. Write their electronic configuration. Which of these will be more electronegative and why ? (CBSE 2012)
Answer:
The electronic configurations of the two elements are :
Nitrogen (Z = 7) 2, 5 ;
Phosphorus (Z = 15) 2, 8, 5
Since the size of nitrogen is small as compared to phosphorus, it has a greater tendency to take up electrons. It is therefore, more electronegative than phosphorus.

Question 8.
How does the electronic configuration of an atom relate to its position in the modern periodic table ?
(CBSE Delhi 2011)
Answer:
The modern periodic table is based upon atomic numbers of the elements. Since electronic configurations of the elements depend upon their atomic numbers, this means that the periodic table is based on the electronic configurations of the elements. For example, all the alkali metals have one electron each in their valence shell. These are placed in group 1. Similarly, the alkaline earth metals with two electrons in their valence shell are placed in group 2 and so on.

Question 9.
In the modern periodic table, calcium (Z = 20) is surrounded by the elements with atomic numbers 12, 19, 21 and 38. Which of these have physical and chemical properties resembling calcium ?
(CBSE All India 2011)
Answer:
Only those elements are placed in the same group in which the gaps of atomic numbers are : 8, 8, 18, 18, 32. If we look at the atomic numbers of the elements that are listed, it becomes clear that the elements with atomic numbers 12, 20 (Ca), 38 fit into this pattern. They are placed in the same group and have also similar physical and chemical properties.

Question 10.
Compare and contrast the arrangement of elements in Mendeleevs periodic table and the modern periodic table.
Answer:
The main points of distinction between Mendeleevs periodic table and Modern periodic table are as follows :

NCERT Solutions for Class 10 Science Chapter 5 – Periodic Classification of Elements

Hope given NCERT Solutions for Class 10 Science Chapter 5 helpful to you.

NCERT Solutions for Class 10 Science Chapter 4 Carbon and its Compounds

In this chapter, students will learn about bonding in carbon –The Covalent Bond, versatile nature of Carbon, saturated and unsaturated carbon compounds, chemical properties of carbon compound, soaps and detergents.

These Solutions are part of NCERT Solutions for Class 10 Science. Here we have given NCERT Solutions for Class 10 Science Chapter 4 Carbon and its Compounds. Learn Insta provides you the Free PDF download of NCERT Solutions for Class 10 Science (Chemistry) Chapter 4 – Carbon and Its Compounds solved by Expert Teachers as per NCERT (CBSE) Book guidelines. All Chapter 4 – Carbon and Its Compounds Exercise Questions with Solutions to help you to revise complete Syllabus and Score More marks.

NCERT Questions

In Text Book Questions

Question 1.
What would be the electron dot structure of carbon dioxide which has the formula CO₂ ?
Answer:
The atomic number (Z) for carbon is six and its electronic configuration is 2, 4. Carbon has four valence
electrons. Each oxygen atom (Z = 8) has six valence electrons (2, 6). In order to complete its octet, the carbon atom shares its four valence electrons with the four electrons of the two oxygen atoms as follows :

Thus, in carbon dioxide molecule, the carbon atom is linked to two oxygen atoms on both sides by two shared pairs of electrons resulting in double bonds on either sides. Both carbon and oxygen atoms complete their octet as a result of electron sharing.

More Resources

• NCERT Solutions for Class 10 Science
• NCERT Exemplar Solutions for Class 10 Science
• HOTS Questions for Class 10 Science
• Value Based Questions in Science for Class 10
• Previous Year Question Papers for CBSE Class 10 Science

Question 2.
What would be the electron dot structure of a molecule of sulphur which is made up of eight atoms of sulphur ?
Answer:
The atomic number (Z) of sulphur is sixteen and its electronic configuration is 2, 8, 6. The sulphur atom has six valence electrons. The chemical formula of sulphur molecule is S₈. Each sulphur atom is linked to similar atoms on either sides by single covalent bonds and thus, completes its octet. The molecule is in the form of a ring also represented by crown shape.
Ring structure of S₈ molecule Crown shape of S₈ molecule

Question 3.
How many structural isomers you can you draw for pentane ?
Answer:
Pentane (C₅H₁₂) has a skeleton of five carbon atoms. It can exist as a straight chain as well as two branched chains. There are three structural isomers for the hydrocarbon which is an alkane.

Question 4.
What are the two properties of carbon which lead to the huge number of carbon compounds we see around us ?
Answer:

1. Catenation: Carbon has the unique property of self linking which is known as catenation. In fact, any number of carbon atoms can be linked to one another by covalent bonds. This is on account of the stability of C—C bonds since the size of the carbon atom is quite small.
2. Linking of carbon with other atoms. Carbon is tetravalent in nature and can readily unite with atoms like hydrogen, oxygen, nitrogen, sulphur etc. by electron sharing.

Question 5.
What will be the formula and electron dot structure of cyclopentane ? (CBSE 2013)
Answer:
Cyclopentane is a cyclic compound with formula C₅H₁₂ The structure of the compound may be represented as :

Question 6.
Draw the structures of the following compounds :
(i) Ethanoic acid
(ii) Bromopentane
(iii) Butanone Are structural isomers possible for bromopentane ?
Answer:

Bromopentane has a chain of five carbon atoms. It can exist in a number of forms which are structural isomers.

The structural isomers (i), (ii) and (iii) which differ in the position of the Br atom are known as position isomers.
The structural isomers (iv), (v) and (vi) which differ in the arrangement of carbon atoms in the chain are called chain isomers.
In writing the IUPAC name, the name of prefix bromo is written before that of prefix methyl. In fact, alphabetical order is followed while naming the different prefixes.

Question 7.
How would you name the following compounds ?

Answer:
(i) Bromoethane
(ii) Hex-l-yne
(iii) Methanal

Question 8.
Why is the conversion of ethanol into ethanoic acid an oxidation reaction ?
Answer:
Ethanoic acid (CH₃COOH) has one oxygen atom more and two hydrogen atoms less than ethanol (C₂H₅OH). In general,

• Loss of hydrogen is known as oxidation.
• Gain of oxygen is known as oxidation.

Therefore, it is an oxidation reaction.

Question 9.
A mixture of ethyne and oxygen is used for welding. Can you tell why a mixture of ethyne and air is not used ?
Answer:
When ethyne is burnt in oxygen, large quantity of heat alongwith light is produced. The heat evolved can be used for gas welding which is usually carried to weld small broken pieces of articles made up of iron.

Air mainly contains a mixture of nitrogen (4 parts) and oxygen (1 part). As we know, nitrogen gas does not support combustion. This means that in air, only oxygen will help in the combustion of ethyne. Therefore, it is always better to use oxygen for the combustion of ethyne.

Question 10.
How would you distinguish experimentally between an alcohol and a carboxylic acid ?
Answer:
The distinction can be made by the following tests :

1. Dip a strip of blue litmus separately in both alcohol and carboxylic add taken in two glass tubes. The colour will change to red in the tube containing carboxylic acid and not in the tube which contains alcohol.
2. Add a small amount of solid sodium hydrogen carbonate (NaHCO₃) in both the tubes. A brisk effervescence accompanied by bubbles will be noticed in the tube containing carboxylic acid and not in the tube containing alcohol.

Question 11.
What are oxidising agents ?
Answer:
Oxidising agents are the substances which either their own or on reacting with another substance release
oxygen in order to carry oxidation reactions. The commonly used oxidising agents are : Ozone, bromine
water, a mixture of potassium dichromate and sulphuric acid or a mixture of potassium permanganate and sulphuric acid etc.

Question 12.
Would you be able to check if water is hard by using a detergent ?
Answer:
No, it is not possible. Actually detergents produce foam in any type of water ; whether hard or soft.
Therefore, a distinction between the two cannot be made. However, soaps can be used for this purpose.

Question 13.
People use a variety of methods to wash clothes. Usually after adding soap, they beat the clothes on a stone or beat them with a paddle, scrub with a brush or the mixture is agitated in a washing machine Why is this agitation necessary to get clean clothes ?
Answer:
The purpose of soap or detergent in washing is to reduce friction between oil drops carrying dirt particles and water so that they may mix with each other. All the methods that have been suggested loosen the bonds between the dust or oil particles and fabrics of clothes. The agitation helps in washing the clothes.

NCERT End Exercise

Question 1.
Ethane, with the molecular formula C₂H₆ has :
(a) G covalent bonds
(b) 7 covalent bonds
(c) 8 covalent bonds
(d) 9 covalent bonds
Answer:

(b). The molecule has seven covalent bonds.

Question 2.
Butanone is a four carbon compound with the functional group
(a) carboxylic acid
(b) aldehyde
(c) ketone
(d) alcohol.
Answer:
(c). The functional group is ketone (>C=0) also known as one.

Question 3.
While cooking, if the bottom of the vessel is getting blackened on the outside, it means that
(a) the food is not cooked completely
(b) the fuel is not burning completely
(c) the fuel is wet
(d) the fuel is burning completely.
Answer:
(b). The fuel is not burning completely. The unburnt particles present in smoke blacken the vessel from outside.

Question 4.
Explain the nature of the covalent bond using the bond formation in CH₃Cl.
Answer:
The molecule of chloromethane (CH₃Cl) consists of three elements i.e., carbon (Z = 6) hydrogen (Z = 1) and chlorine (Z = 17). Carbon atom has four valence electrons (2, 4) ; hydrogen has one (1) while chlorine has seven electrons in the valence shell (2, 8, 7). In order to complete its octet, carbon shares three valence electrons with three hydrogen atoms while one is shared with the electron of chlorine atom. The structure of covalent molecule may be written as follows :

Question 5.
Draw the electron dot structures for
(i) ethanoic acid
(ii) H₂S
(iii) propanone
(iv) F₂.
Answer:

Question 6.
What is homologous series ? Explain with an example.
Answer:
A series of similarly constituted compounds in which the members present have the same functional group, same chemical properties and any two successive members in a particular series differ in their molecular formula by —CH₂ group and molecular mass by 14 u.
For example, the boiling points of members in the family of alkanes follow the order :

Question 7.
How can ethanol and ethanoic acid be differentiated on the basis of their physical and chemical properties ?
(CBSE Delhi 2011)

Answer:
Distinction based on physical properties :

1. Smell. Ethanol has a characteristic smell known as alcoholic smell which is pleasant. Ethanoic acid has vinegar like smell.
2. Boiling points. Boiling point of ethanol (351 K) is less than that of ethanoic acid (391 K).
3. Litmus test. Ethanol is neutral in nature and does not bring any change in the colour of litmus whether blue or red. Ethanoic acid is acidic and changes the colour of a blue litmus strip to red when dipped in it.

Distinction based on chemical properties :

1. Action with sodium hydrogen carbonate. On adding a small amount of sodium hydrogen carbonate to ethanoic acid, carbon dioxide gas is evolved with brisk effervescence. However, no such reaction is noticed in case of ethanol.
   CH₃COOH + NaHCO₃ ———> CH₃COONa + CO₂ + H₂O
2. Action with caustic alkalies. Ethanoic reacts with both sodium hydroxide (NaOH) and potassium hydroxide (KOH) to form corresponding salt and water. Ethanol fails to react with either of these.
   

Question 8.
Why does micelle formation take place when soap is added to water ? Will a micelle be formed in other solvents such as ethanol also ? (CBSE Delhi 2011)
Answer:
Soap may be represented by the formula RCOO^–Na⁺ where R is an alkyl group which represents long chain of carbon with fifteen or more atoms. Now, oil drops containing dirt particles and water donot mix. Soap helps in their mixing by reducing interfacial tension or friction. Actually it forms a sort of bridge between oil drops and water in which the alkyl portion (hydrophobic end) points towards oil drop while other portion COONa (hydrophilic end) is directed towards water. This is known as micelle formation. Thus, soap helps in the formation of a stable emulsion between oil and water. Ethanol and other similar solvents which are of organic nature, donot help in micelle formation because soap is soluble in them.

Question 9.
Why are carbon and its compounds used as fuels in most cases ?
Answer:
Carbon burns in oxygen or air to form carbon dioxide gas. The reaction is highly exothermic. That is why different forms of coal are used as fuels. The most important compounds of carbon are hydrocarbons. Just like carbon, hydrogen also readily burns in oxygen or air to form water producing heat. The hydrocarbon methane (CH₄) is a constituent of natural gas. Propane (C₃H₈) and butane (C₄H₁₀) are present in liquid petroleum gas (L.P.G.). Petrol and kerosene also contain different hydrocarbons. Therefore, these are used as fuels.

Question 10.
Explain the formation of scum when hard water is treated with soap. (CBSE Delhi 2011)
Answer:
Soap is basically sodium or potassium salt of higher fatty acids. Hard water contains in it Ca²⁺ and Mg²⁺ ions as their salts. When soap is added to hard water, the corresponding calcium and magnesium salts are formed. These are in the form of precipitates, also called ‘scum’.

Question 11.
What change will you observe by testing soap with litmus paper (blue or red) ?
Answer:
When soap is dissolved in water, the solution is alkaline in nature due to the formation of alkali NaOH or KOH. The solution changes the colour of red litmus to blue. However, the solution does not change the colour of blue litmus.

Question 12.
What is hydrogenation ? What is its industrial application ?
Answer:
The addition of hydrogen to unsaturated hydrocarbon in the presence of a metal catalyst is also known as catalytic hydrogenation.
The reaction is extremely useful in the hydrogenation of vegetable oils also called edible oils e.g. ground nut oil, cotton seed oil etc. These are also called cooking oils and are unsaturated in the sense that their molecules contain atleast one C=C bond in their structures. Upon passing hydrogen gas through oil in the presence of nickel catalyst, the double bond changes to single bond. As a result, the unsaturated oil changes to solid fat which is of saturated nature. Vegetable ghees such as Dalda, are of saturated nature and are formed by catalytic hydrogenation reaction.

Question 13.
Which of the listed hydrocarbons undergo addition reactions : C₂H₆, C₃H₈, C₃H₆, C₂H₂ and CH₄ ?
Answer:
In order that a hydrocarbon may undergo addition reaction, it must be unsaturated in nature. It must be either an alkene (C=C) with general formula C_nH_2n or an alkyne (C = C) with general formula C_nH_2n-2. Out of the list of the hydrocarbons given :

• C₃H₆ (Propene) is an alkene with C=C bond. It corresponds to general formula C_nH_2n (n = 3)
• C₂H₂ (Ethyne) is an alkyne with C = C bond. It corresponds to general formula C_nH_2n-2 (n = 2).

Both these hydrocarbons take part in addition reactions. For example, they react with hydrogen upon heating to 473 K in the presence of Nickel catalyst to form corresponding alkanes.

Question 14.
Give a test that can be used to differentiate between butter and cooking oil.
Answer:
Butter is saturated in nature while cooking oil is unsaturated. This means that cooking oil has atleast one C=C bond present in the constituting compounds while butter does not have any such bond. The distinction between them can be made by reacting with bromine water or bromine dissolved in carbon tetrachloride. Cooking oil will discharge the yellow colour of bromine while butter will not.

Question 15.
Explain the mechanism of cleansing action of soap.
Answer:
Cleansing action of Soaps and Detergents
Both soaps and detergents resemble in their cleansing action. They have two main parts. These are non—polar hydrocarbon chain which is water repellent or hydrophobic (phobic or phobia stands for repulsion or hatred) and the polar carboxyl group as its salt which is attracted towards water or is hydrophilic (philic stands for love or attraction). The former is called the tail of the molecule and the latter is regarded as the head.

In order to understand the cleansing action of both soaps and detergents, let us try to analyse how the clothes become dirty. They first become oily because of the perspiration coming out of the skin and also from the organic matter dispersed in the atmosphere. Dust particles stick to oil drops and the clothes become dirty. In order to wash these, they are dipped in water and soap or detergent is applied. In solution, it dissociates to give carboxylate ions (RCOO ) or sulphonate ions (RSO₃^–) and the cations (Na⁺). In the carboxylate ion, the alkyl portion which contains a long chain of hydrocarbons is a tail pointing towards the oil drops while the COO^– portion is the head directed towards water. In a detergent it is the SO₃^– portion which points towards water. This is quite evident from the figure where the solid circles (•) represent the polar groups and the wavy lines (^^^) represent the alkyl portions. The molecules of soap or detergent have a unique orientation in water. They actually form a cluster of molecules in which the hydrophobic or alkyl portion is in the interior while the ionic or polar portion is on the surface of the cluster as shown in the figure. This formation is known as micellear formation or simply micelle. Soaps or detergent thus help in forming a stable emulsion of oil and water by acting as a bridge between the two. The oil droplets alongwith the particles of the dirt get detached from the fibres of the clothes and pass into the emulsion. In this manner, the clothes become free from dust or dirt.

NCERT Solutions for Class 10 Science Chapter 4 Carbon and Its Compounds

Hope given NCERT Solutions for Class 10 Science Chapter 4 helpful to you.

NCERT Solutions for Class 10 Science Chapter 3 Metals and Non-metals

In this chapter, students will learn about the physical properties of metals, and non-metals, chemical properties of metals, how metals react with air, water, acid, other solutions, and metal salts, reactivity series.

Further students will come to know how metals and non-metals react, properties of ionic compounds, the occurrence of metals, extraction of metals, refining of metals, corrosion, prevention of corrosion. The chapter contains questions and answers exercise along with multiple choice questions.

These Solutions are part of NCERT Solutions for Class 10 Science. Here we have given NCERT Solutions for Class 10 Science Chapter 3 Metals and Non-metals. LearnInsta.com provides you the Free PDF download of NCERT Solutions for Class 10 Science (Chemistry) Chapter 3 – Metals and Non-metals solved by Expert Teachers as per NCERT (CBSE) Book guidelines. All Chapter 3 – Metals and Non-metals Exercise Questions with Solutions to help you to revise complete Syllabus and Score More marks.

NCERT Solutions for Class 10 Science Chapter 3 NCERT Questions

NCERT Solutions for Class 10 Science Chapter 3 In Text Book Questions

Question 1.
Give example of a metal which
(a) is a liquid at room temperature
(b) can be easily cut with a knife
(c) is the best conductor of heat
(d) is the poorest conductor of heat.
Answer:
(a) Mercury
(b) Sodium
(c) Silver
(d) Lead.

More Resources

• NCERT Solutions for Class 10 Science
• NCERT Exemplar Solutions for Class 10 Science
• HOTS Questions for Class 10 Science
• Value Based Questions in Science for Class 10
• Previous Year Question Papers for CBSE Class 10 Science

Question 2.
Explain the meaning of malleable and ductile.
Answer:
Malleable: The property due to which a substance can be beaten into sheets is known as malleability. Metals are malleable in nature.
Ductile. The property due to which a substance can be drawn into wires is known as ductility. Metals are ductile in nature.

Question 3.
Why is sodium kept immersed in kerosene oil ? (CBSE 2011)
Answer:
Sodium reacts with air and water both. It is a highly reactive metal. When kept in open, it readily combines with oxygen present in air to form its oxide. Similarly, it reacts with water vapours or moisture to form sodium hydroxide.

In order to preserve sodium metal, we generally keep it under kerosene so that neither air nor moisture may come in its contact.

Question 4.
Write the equations for the reactions of
(a) iron with steam
(b) calcium with water
(c) potassium with water.
Answer:
(a) 3Fe(s) + 4H₂O (steam) ———–> Fe₃O₄(s) + 4H₂(g)
(b) Ca(s) + 2H₂O(aq) ———–> Ca(OH)₂(s) +H₂(g)
(c) 2K(s) + 2H₂O(aq) ———–> 2KOH(aq) + H₂(g)

Question 5.
Samples of four metals A, B, C and D were taken and were added to the following solutions one by one. The results obtained have been tabulated as follows :

Use the table given above to answer the following questions :
(a) Which is the most reactive metal ?
(b) What would you observe when B is added to solution of copper(II) sulphate ?
(c) Arrange the metals A, B, C and D in order of increasing reactivity. (CBSE 2011)
Answer:
Based on the activity series, the relative position of the metals in which involved in solutions is : Zn > Fe > Cu > Ag. On the basis of the results given in the table .

• Metal A is more reactive than copper and less reactive than iron.
• Metal B is more reactive than iron and less reactive than zinc. –
• Metal C is only more reactive than silver and less reactive than other metals.
• Metal D is the least reactive in nature.

In the light of above information, we can conclude that
(a) Metal B is the most reactive.
(b) Since B is more reactive than iron, it is also more reactive than copper. This means that it would displace copper from copper(II) sulphate solution. The blue colour of solution will slowly fade.
(c) The decreasing order of reactivity of metals is: B>A>C>D.

Question 6.
Which gas is produced when a reactive metal reacts with dilute hydrochloric acid ? Write the chemical reaction when iron reacts with dilute H₂SO₄. (CBSE 2010)
Answer:
Hydrogen gas (H₂) is produced when a reactive metal reacts with dilute hydrochloric acid. Iron and dilute H₂SO₄ react as follows :
Fe(s) + H₂SO₄(aq) ————> FeSO₄(aq) + H₂(g)
Hydrogen gas is evolved in this reaction also.

Question 7.
What would you observe when zinc is added to a solution of iron (II) sulphate ? Write the chemical reaction that takes place. (CBSE 2010)
Answer:
The green colour of the solution would slowly disappear. Zinc would gradually dissolve and iron would get precipitated at the bottom of the beaker.

Question 8.
(i) Write electron-dot structures for sodium, magnesium and oxygen.
(ii) Show the formation of Na₂O and MgO by the transfer of electrons.
(iii) What are the ions present in these compounds ?
Answer:
(i)

(ii) Formation of sodium oxide (Na₂O)

Formation of magnesium oxide (MgO)

(iii) For answer, consult structures given above.

Question 9.
Why do ionic compounds have high melting points ? (CBSE 2014)
Answer:
In the formation of ionic compounds, positive ions (cations) and negative ions (anions) participate. These are closely packed and the ionic compounds exist as crystalline solids. They have strong inter ionic forces of attraction and have high melting and boiling points.

Question 10.
Define the following terms :

1. Minerals
2. Ores
3. Gangue.

Answer:

1. Minerals : These are the combined states of metals and non-metals present in earth’s curst.
2. Ores : The minerals from which metals can be conveniently and profitably extracted, are called ores.
3. Gangue : It represents the earthy impurities such as mud, sand and clay associated with the ore.

Question 11.
Name two metals which are formed in nature in free state.
Answer:
The metals are gold (Au) and platinum (Pt).

Question 12.
Which chemical process is used for obtaining a metal from its oxide ?
Answer:
The chemical process is known as reduction.

Question 13.
Metallic oxides of zinc, magnesium and copper were heated with the following metals. In which cases, will you find displacement reactions taking place ?

Relative positions of these metals in the activity series are : Mg, Zn, Cu : In the light of this :
Answer:
Magnesium (Mg) will displace both zinc (Zn) and copper (Cu) from their oxides
Mg + ZnO ———-> MgO + Zn
Mg + CuO ———-> MgO + Cu
Zinc will displace copper from copper oxide.
Zn + CuO ———–> ZnO + Cu
Copper is least reactive and will not initiate displacement reaction.

Question 14.
Which metals do not corrode easily ?
Answer:
Metals such as gold (Au) and platinum (Pt) present at the bottom of the activity series do not corrode easily.

Question 15.
What are alloys ? (CBSE 2011)
Answer:
Alloys are the homogeneous mixture of two or more metals or even metals and non-metals.

NCERT Solutions for Class 10 Science Chapter 3 NCERT End Exercise

Question 1.
Which of the following will give displacement reactions ?
(a) NaCl solution and copper metal
(b) MgCl₂ solution and aluminium metal
(c) FeSO₄ solution and silver metal
(d) AgNO₃ solution and copper metal.
Answer:
(d). Only AgNO₃ solution will give displacement reaction with copper (Cu) because copper is placed above silver in the activity series.

Question 2.
Which of the following methods is suitable for preventing an iron frying pan from rusting ?
(a) applying grease
(b) applying paint
(c) applying a coating of zinc
(d) all the above.
Answer:
Theoretically all the three methods are helpful for preventing an iron frying pan from rusting. However, the constituents of both grease and paint are mostly organic compounds. They cannot withstand the heat and do not last. Therefore, applying a coating of zinc (galvanisation) is the best method. Option (c) is correct.

Question 3.
An element reacts with oxygen to give a compound with high melting point. This compound is also water soluble. The element is likely to be :
(a) Calcium
(b) Carbon
(c) Silicon
(d) Iron
Answer:
(a). Calcium (Ca) combines with oxygen to form calcium oxide (CaO) with very high melting point. CaO dissolves in water to form calcium hydroxide

Question 4.
Food cans are coated with tin and not with zinc because
(a) Zinc is costlier than tin
(b) Zinc has higher melting point than tin
(c) Zinc is more reactive than tin
(d) Zinc is less reactive than tin.
Answer:
(c). Zinc is more reactive than tin and reacts with organic acids present in food to form poisonous compounds. Since tin is placed below zinc in the activity series, it is less reactive and does not react with the organic acids. Therefore, (c) is the correct option.

Question 5.
You are given a hammer, a battery, a bulb, wires and a switch :
(a) Flow could you use them to distinguish between samples of metals and non metals ?
(b) Assess the usefulness of these tests to distinguish between metals and non metals.
Answer:
(a) With the help of hammer, convert both the metal and non-metal (solid) in the form of plates or rods. Metal will readily form these since they are malleable. Non-metals being brittle will break when struck with hammer. They will form plates with difficulty Now construct a cell in both the cases using these plates as electrodes and switch on the current. If the bulb glows, this means that the electrodes are of metals. In case, this does not glow, this means that the electrodes are of non-metals.
(b) From these tests, we may conclude that

1. Metals are malleable while non-metals are not.
2. Metals are good conductors of electricity while non-meals are not (graphite is an exception).

Question 6.
What are amphoteric oxides ? Give examples of two amphoteric oxides.
Answer:
These are the oxides which can act both as acids and bases. For example, aluminium oxide (Al₂O₃) and zinc oxide (ZnO). The amphoteric character of the two oxides are shown by the following reactions.

Question 7.
Name two metals which can displace hydrogen from dilute acids and two metals which can not do so.
Answer:
Sodium and calcium can displace hydrogen from dilute acids Copper and silver can not displace hydrogen from dilute acids.

Question 8.
In the electrolytic refining of metal M, name anode, cathode and electrolyte.
Answer:
Anode : Rod of the impure metal
Cathode : Rod of pure metal
Electrolyte : Aqueous solution of soluble salt of metal M.

Question 9.
Pratyush took sulphur powder on a spatula and heated it. He collected the gas evolved by inverting a test tube over it as shown in the figure.

What will be the action of gas on

1. dry litmus paper ?
2. moist litmus paper ?

Write a balanced chemical equation for the reaction taking place.
(CBSE 2011)
Answer:
The gas evolved upon heating sulphur powder on a spatula is sulphur dioxide

1. SO₂(g) has no action of dry litmus paper.
2. SO₂(g) dissolves in moisture (water) present in moist litmus paper to form sulphurous acid. In acidic solution, moist litmus paper will change to red.
   

Question 10.
State two ways to prevent the rusting of iron.
Answer:

1. By applying a coating of grease or paint on the surface of iron.
2. By depositing a layer of zinc on the surface of iron. The process is called galvanisation.

Question 11.
What types of oxides are formed when non-metals combine with oxygen ?
Answer:
The oxides are generally acidic in nature which means that when dissolved in water, their solutions change blue litmus to red. For example,

Question 12.
Give reasons for the following :
(a) Platinum, gold and silver are used to make jewellery.
(b) Sodium, potassium and lithium are stored under oil.
(c) Aluminium is a highly reactive metal but still used for making cooking utensils.
(d) Carbonate and sulphide ores are usually converted into oxides during the process of extraction. (CBSE 2013, 2014)
Answer:
(a) These metals placed at the bottom of the activity series are very little reactive in nature. Gold and
platinum are known as noble metals. They are not affected by air, water and by chemicals. Since they have bright lustre, jewellery can be made from these metals.
(b) There are reactive metals placed high in the activity series. In air, their surface gets tarnished due to presence oxygen, water vapours and carbon dioxide in air. With water, these react violently to evolve so much heat that is not possible to handle them. These metals are generally kept under kerosene which does not contain air and water.
(c) When exposed to air, the metal changes its oxide called aluminium oxide (Al₂CO₃). It gets deposited over the surface of the metal and forms a protective coating on the surface. Due to the presence of this layer, the metal becomes unreactive and can be used in making cooking utensils.
(d) Both carbonate and sulphide ores of metals cannot be directly reduced to metallic state. Flowever, metal oxides can be easily reduced with coke or other reducing agents. Both are therefore, converted into their respective oxides by calcination process (for carbonate ores) and by roasting process (for sulphide ores).
Metal oxides can be easily reduced to metallic form with coke (C) or any other suitable reducing agent. Therefore, carbonates and sulphides are converted to the oxide form by processes of calcination and roasting and are not directly reduced.

Question 13.
You must have seen tarnished copper vessels being cleaned with lemon or tamarind juice. Explain why these sour substances are effective in cleaning the vessels. (CBSE 2014)
Answer:
Copper metal slowly reacts with water, carbon dioxide and oxygen present in air to form basic copper carbonate which is green in colour. Its layer slowly gets deposited on the surface of the metal. Now lemon

juice contains citric acid while tartaric acid is present is tamrind. Both these acids react with basic copper carbonate to form soluble salts such as copper acetate (with citric acid) and copper tartarate (with tartaric acid). The equations for the reactions are complicated and are not given. These salts are removed from the surface of the copper metal and the surface of the metal shines.

Question 14.
A man went door to door posing as a goldsmith. He promised to bring back the glitter on dull gold ornaments. An unsuspecting lady gave a set of gold bangles to him which he dipped in a particular solution. The bangles sparked like new but their weight was reduced drastically. The lady got upset and after a futile argument, the man beat a hasty retreat. Can you predict the nature of the solution used by the impositer ?
Answer:
The man had actually used the solution of aqua regia (mixture of cone. HCl and cone. HNO₃ in the ratio of 3 : 1 by volume) which has dissolved gold forming soluble auric chloride (AuCl₃). Since gold actually reacted, there was a loss in weight of the gold bangles. With the removal of the dull layer of gold from the surface, there was original shine on the bangles. The chemical reactions have been

Question 15.
Give reason as to why copper is used to make hot water tanks and not steel (an alloy of iron).
Answer:
Copper is a better conductor of heat than steel which is an alloy of iron. Though copper is costlier than steel, it is used to make hot water tanks for storing hot water in preference to steel.

Question 16.
Differentiate between metals and non-metals on the basis of chemical properties.
For the distinction in the chemical characteristics,

Hope given NCERT Solutions for Class 10 Science Chapter 3 are helpful to complete your science homework.

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NCERT Solutions for Class 10 Science Chapter 3 Metals and Non-metals

NCERT Solutions for Class 10 Science Chapter 2 Acids Bases and Salts

In this chapter, students will understand the chemical properties of acids, and bases, how acids and bases react with metals, how metal carbonates, and metal hydrogen carbonates react with acids, how acids and bases react with each other, the reaction of metallic oxides with acids. Students will also learn about what all acids and bases have in common, what happens to acids and bases in water solution, the importance of pH in everyday life, pH of salts.

These Solutions are part of NCERT Solutions for Class 10 Science. Here we have given NCERT Solutions for Class 10 Science Chapter 2 Acids Bases and Salts. LearnInsta.com provides you the Free PDF download of NCERT Solutions for Class 10 Science (Chemistry) Chapter 2 – Acids, Bases and Salts solved by Expert Teachers as per NCERT (CBSE) Book guidelines. All Chapter 2 – Acids, Bases and Salts Exercise Questions with Solutions to help you to revise complete Syllabus and Score More marks.

NCERT Solutions for Class 10 Science Chapter 2 In Text Book Questions

Question 1.
You have been provided with three test tubes. One of them contains distilled water and the other two contain an acidic solution and a basic solution respectively. If you are given only red litmus paper, how will you identify the contents of each test tube ?
Answer:
Take a small volume of all the three liquids in three test tubes. Dip red litmus paper strips separately in all the three. The tube in which red litmus strip turns blue, contains basic solution. Now remove the blue litmus paper and dip it one of the remaining test tubes. If the colour of the blue litmus paper changes to red, the tube contains acidic solution. In case, it remains blue then the tube contains distilled water.

More Resources

• NCERT Solutions for Class 10 Science
• NCERT Exemplar Solutions for Class 10 Science
• HOTS Questions for Class 10 Science
• Value Based Questions in Science for Class 10
• Previous Year Question Papers for CBSE Class 10 Science

Question 2.
Why should not curd and sour substances be kept in containers made up of brass or copper ?
Answer:
Both curd and sour substances contain some acids in them. They react with copper or brass vessels to form certain salts which are of poisonous nature. Therefore, it is not advisable to keep them in these containers.

Question 3.
Which gas is usually liberated when an acid reacts with a metal ? Illustrate with an example. How will you test the presence of this gas ?
Answer:
Metals are mostly reactive in nature. They react with dilute acids (HCl and H₂SO₄) to evolve hydrogen gas. For example,

The gas burns with a pop sound when a burning candle is brought near it.

Question 4.
A metallic compound ‘A’ reacts with dilute hydrochloric acid to produce effervescence. The gas evolved extinguishes a burning candle. Write a balanced chemical equation for the reaction if one of the compounds formed is calcium chloride.
Answer:
Since the gas is evolved with effervescence and extinguishes fire, it is expected to be CO₂ gas. As calcium chloride is formed as one of the products, this means that the substance A’ can be calcium carbonate. It reacts with dilute hydrochloric acid as :

Question 5.
Aqueous solutions of HCl, HNO₃ and H₂SO₄ etc. show acidic character while those of the compounds like ethyl alcohol (C₂H₅OH) and glucose (C₆H₁₂O₆) fail to do so. Explain.
Answer:
All the acids that are listed, have replaceable hydrogen atoms which they release in aqueous solution as H⁺ ions. Therefore, they show acidic character. However, both ethyl alcohol (C₂H₅OH) and glucose (C₆H₁₂O₆) do not have replaceable hydrogen atoms. They fail to evolve hydrogen gas and do not show any acidic character.

Question 6.
Why does aqueous solution of an acid (HA) conduct electricity ?
Answer:
Aqueous solution of an acid (HA) releases H+ ions or H₃O⁺ ions and anions (A^–) in solution. Since ions are the carrier of charge, the aqueous solution of an acid conducts electricity.

Question 7.
Why does not dry HCl gas change the colour of the dry litmus paper ? (CBSE 2013)
Answer:
Dry HCl gas fails to release any H⁺ ions which means that it is not acidic. It fails to change the colour of the dry litmus paper which has also no moisture present.

Question 8.
While diluting an acid, why is it not recommended that acid should be added to water and not water to the acid ? (CBSE 2011)
Answer:
Acids particularly the mineral acids like H₂SO₄, HNO₃ and HCl etc., have strong affinity for water. The dilution process is highly exothermic in nature. The heat evolved may crack or break the container and may also convert the acid into fog which is likely to pollute the atmosphere. In order to control the heat evolved, it is advisable to add acid drop by drop to water. In case water is added to acid, then the entire acid will get itself involved in the exothermic process. It may not be possible to control the heat evolved.

Question 9.
How is concentration of hydronium ions (H₃O⁺) affected when solution of an acid is diluted with water ?
Answer:
An acid dissociates into hydronium ions (H₃O⁺) and anions when dissolved in water. Upon dilution, the volume of the solution increases and the number of ions per unit volume decreases. Therefore, the concentration of H₃O⁺ ions per unit volume decreases.

Question 10.
How is concentration of hydroxyl (OH^–) ions affected when excess of base is dissolved in solution of sodium hydroxide ?
Answer:
Sodium hydroxide (NaOH) is a strong base. It immediately dissociates in solution to give OH^– ions and cations. Upon dissolving more of base in the solution, the concentration of OH^– ions further increases.

Question 11.
You have two solutions A and B. The pH of solution A is 6 and that of solution B is 8. Which solution has more hydrogen ion concentration ? Which of these is acidic and which one is basic ?
Answer:
The pH of a solution is inversely proportional to the concentration of H⁺ ions in solution. Lesser the pH of the solution, more will be the H⁺ ion concentration. The solution A with pH 6 has more H⁺ ion concentration than the solution with pH equal to 8. The solution A is acidic because its pH is less than 7 and the solution B is basic because its pH is more than 7.

Question 12.
What effect does concentration of H⁺(aq) ions have on acidic nature of absolution ?
Answer:
The acidic nature of a solution is directly related to the concentration of H⁺ ions. As the concentration of H⁺ ions increases, the acidic nature of solution also increases.

Question 13.
Do basic solutions also have H⁺(aq) ions ? If yes, then why are these basic ?
Answer:
Yes, basic solutions have also H⁺(aq) ions present in them. Actually, these solutions are prepared in water. Being a weak electrolyte, it dissociates to give H⁺ and OH^– ions. However, the number of H⁺ ions is very small as compared to the number of OH^– ions which are released by the base and also by water. Therefore, the solutions as a whole are of basic nature.

Question 14.
Under what soil conditions, do you think a farmer would spread or treat the soil of his fields with quick lime (calcium oxide) or slaked lime (calcium hydroxide) or chalk (calcium carbonate) ?
Answer:
A soil usually becomes acidic when there is either a high peat content, iron minerals or there is some rotting vegetable. In order to reduce the acidic strength, ‘liming of soil’ is usually done. For this, any of the substances that have been mentioned are added to the soil since these are of basic nature.

Question 15.
Name the substance which upon treating with chlorine gives bleaching powder. Write the chemical equation for the reaction. (CBSE 2011)
Answer:
Slaked lime is the substance which reacts with chlorine to give bleaching powder

Question 16.
Name the sodium compound used for softening hard water.
Answer:
Washing soda or sodium carbonate. It is chemically sodium carbonate decahydrate (Na₂CO₃.10H₂O). What will happen if the solution of sodium hydrogen carbonate is heated ?

Question 17.
Write the chemical equation involved.
Answer:
Carbon dioxide gas will evolve and sodium carbonate will be left.

Question 18.
Write the chemical equation for the reaction between Plaster of Paris and water.
Answer:

NCERT Solutions for Class 10 Science Chapter 2 NCERT End Exercise

Question 1.
A solution turns red litmus blue. Its pH is likely to be
(a) 2
(b) 4
(c) 7
(d) 10.
Answer:
The solution is basic. Its pH is likely to be 10.
Therefore, (d) is the correct answer.

Question 2.
A solution reacts with crushed egg-shells to give a gas that turns lime water milky. The solution contains
(a) NaCl
(b) HCl
(c) LiCl
(d) KCl.
Answer:
The crushed egg-shells consist of layer of calcium carbonate which reacts with dilute HCl to evolve CO₂(g). The gas turns lime water milky.
Therefore (b) is the correct choice.

Question 3.
10 mL of a solution of NaOH is found to be completely neutralised by 8 mL of a given solution of HCl. If we take 20 mL of the same solution of NaOH, the volume of HCl solution (the same solution as before) required to neutralise will be
(a) 4 mL
(b) 8 mL
(c) 12 mL
(d) 16 mL.
Answer:
10 mL of NaOH will require HCl = 8 mL and 20 mL of NaOH will require HCl=16 mL.
Therefore, (d) is the correct answer.

Question 4.
Which of the following types of medicines is used for treating indigestion ?
(a) Antibiotic
(b) Analgesic
(c) Antacid
(d) Antiseptic.
Answer:
Antacid is used for treating indigestion.
The correct answer is (c).

Question 5.
Write the word equations and the balanced equations for the reactions when :
(a) dilute sulphuric acid reacts with zinc granules.
(b) dilute hydrochloric acid reacts with magnesium ribbon.
(c) dilute sulphuric acid reacts with aluminium powder.
(d) dilute hydrochloric acid reacts with iron fillings.
(d) dilute hydrochloric acid reacts with iron fillings.
Answer:

Question 6.
Compounds like alcohol and glucose also contain hydrogen but are not characterised as acids. Describe an activity to prove it.
The chemical formula of ethyl alcohol is C₂H₅OH which is an alcohol and of glucose is C₆H₁₂O₆. Both are organic compounds and contain hydrogen atoms. However, they do not behave as acids. (CBSE 2011, 2013)
Answer:
This can be shown by the following activity :
In a glass beaker, take a dilute solution of glucose (C₆H₁₂O₆). Fix two small nails of iron in a rubber cork and place the cork in the beaker as shown in the figure. Connect the nails to the terminals of a 6 volt battery through a bulb. Switch on the current. The bulb will not glow. This shows that the electric current has not passed through the glucose solution. As the current is carried by the movement of ions, this shows that in solution, glucose has not given any H⁺ ions.

Now repeat the same experiment with ethyl alcohol (C₂H₅OH). The bulb will not glow in this case also. This shows that both of them do not behave as acids although they contain hydrogen atoms in their molecules.

Question 7.
Why does not distilled water conduct electricity whereas rain water does ?
Answer:
Pure water (or distilled water) is a very weak electrolyte and does not dissociate into ions. Therefore, it does not conduct electricity. However, rain water contains some dissolved acids like carbonic acid (H₂CO₃) and sulphurous acid (H₂SO₃). Actually air contains traces of both CO₂ and SO₂ gases which dissolve in rain water to produce corresponding acids. As a result, water becomes acidulated and gets ionised easily. Therefore, rain water conducts electricity.

Question 8.
Why does not an acid show any acidic behaviour in the absence of water ?
Answer:
An acid gets ionized only in aqueous solution i.e. in the presence of water. In other words, an acid releases H+ ions or shows acidic behaviour only in the presence of water.

Question 9.
Five solutions A, B, C, D and E when tested with universal indicator show pH as 4, 2, 12, 7 and 9 respectively. Which solution is :
(a) neutral
(b) strongly alkaline
(c) strongly acidic
(d) weakly alkaline
(e) weakly acidic
(f) Arrange the pH in increasing order of H⁺ ion concentration.
Answer:
(a) Neutral : D with pH = 7
(b) Strongly alkaline : C with pH = 12
(c) Strongly acidic : B with pH =2
(d) Weakly alkaline : E with pH = 9
(e) Weakly acidic : A with pH = 4
(f) Increasing order of H+ ions concentration :C<E<D<A<B

Question 10.
Equal lengths of magnesium ribbons are taken in test tubes A and B. Hydrochloric acid (HCl) is added to test tube A while acetic acid (CH₃COOH) is added to test tube B. In which case, fizzing occurs more vigorously and why ?
Answer:
Fizzing in the reaction is due to the evolution of hydrogen gas by the action of metal on the acid

Since hydrochloric acid is a stronger acid than acetic acid, fizzing occurs more readily in tube A than in tube B. Actually hydrogen gas will evolve at more brisk speed in test tube A.

Question 11.
Fresh milk has a pH of 6. How do you think the pH will change as it turns into curd ? Explain your answer. (CBSE 2011)
Answer:
When milk changes into curd, the pH decreases. Actually, lactose (carbohydrate) present in milk gets converted into lactic acid. As more of acid is formed, pH of the medium decreases.

Question 12.
A milkman adds a very small amount of baking soda to fresh milk.
(a) Why does he shift the pH of the fresh milk from 6 to slightly alkaline ?
(b) Why does this milk take a long time to set as curd ? (CBSE 2011)
Answer:
(a) We know that fesh milk is slightly acidic due to presence of lactic acid and its pH is 6. Upon
standing, its pH slowly decreases and it becomes sour since more of acid to released. The purpose of adding baking soda or sodium hydrogen carbonate (NaHCO₃) is to make medium slighly alkaline. The base released will neutralise the effect of lactic acid present in milk. This will check the milk from getting sour.
(b) When milk sets as curd, it becomes more acidic and pH decreases. In the alkaline medium, it takes longer time to achieve acidic medium back so that milk may set as curd.

Question 13.
Why should Plaster of Paris be stored in a moisture-proof container ?
Answer:
In the presence of moisture, Plaster of Paris gets hydrated and changes to Gypsum which is a hard mass.

It can be no longer be used for making moulds and statues. Therefore, Plaster of Paris is kept in moisture proof containers or bags.

Question 14.
What is neutralisation reaction ? Give two examples.
Answer:
Neutralisation reaction is the reaction between acid and base dissolved in aqueous solution to form salt and water.

Question 15.
Both NaCl and KNO₃ are neutral in nature. They neither change blue litmus red nor red litmus blue. That is why the reaction is called neutralisation reaction.
Give two important uses of washing soda and baking soda. (CBSE 2011)
Answer:
Uses of washing soda:

1. In the manufacture of glass, soap, paper and chemicals like caustic soda (NaOH) and borax (Na₂B₄O₇) etc.
2. As a cleansing agent for domestic purposes.

Uses of baking soda:

1. In baking powder used for preparing cakes.
2. In antacids to reduce acidity in the stomach.

NCERT Solutions for Class 10 Science Chapter 2 Acids, Bases and Salts