Important Questions for CBSE Class 10 Science Chapter 4 - Carbon and Its Compounds

Very Short Answer Questions                                                                  (1 Mark)

1. Soaps are formed by the saponification of

1. Alcohols

2. Simple ester

3. carboxylic acids

4. glycerides

 Ans: d. glycerides

2. The functional group of butanone is

1. Carboxyl

2. Ketonic

3. Aldehydic

4. Alcoholic

Ans: b. ketonic

3. The enzyme which converts starch into glucose is

1. Zymase

2. Maltase

3. Diastase

4. Invertase

Ans: a. Zymase

4. The first compound to be prepared in the laboratory was

1. Methane

2. Ethyl alcohol

3. Acetic acid

4. Urea

Ans: d. Urea

5. The IUPAC name of $C{{H}_{3}}CHO$  is

1. Acetaldehyde

2. Formaldehyde

3. Methyl formaldehyde

4. Ethanol

Ans: d.Ethanol 

6. Rectified spirit is

1. \[\text{50 }\!\!\%\!\!\text{ }\] ethanol

2. \[\text{N80 }\!\!\%\!\!\text{ }\] ethanol

3. \[\text{95 }\!\!\%\!\!\text{ }\] ethanol

4. \[40\% to 50\%\] ethanol

Ans: c. \[\text{95 }\!\!\%\!\!\text{ }\] ethanol

7. Dilute alkaline solution $KMn{{O}_{4}}$ is

1. an oxidizing agent

2. a reducing agent

3. a bleaching agent

4. none of these

Ans: a. an oxidizing agent

8. The by-product in the soap industry is

1. Isoprene

2. Ethylene glycol

3. Glycerol

4. Butane

Ans: c. Glycerol

9. An example of soap is

1. ${{C}_{15}}{{H}_{31}}COONa$  

2. $C{{H}_{3}}COONa$ 

3. ${{C}_{6}}{{H}_{5}}COONa$ 

4. ${{C}_{17}}{{H}_{35}}OS{{O}_{3}}Na$ 

Ans: a. ${{C}_{15}}{{H}_{31}}COONa$ 

10. The number of \[\mathbf{C}-\mathbf{H}\] bonds in ethane ${{C}_{2}}{{H}_{6}}$  molecule are

1. $4$ 

2. $6$ 

3. $8$ 

4. $10$ 

Ans: b. 6

11. The odour of acetic acid resembles that of

1. Rose

2. Burning Plastic

3. Vinegar

4. Kerosene

Ans: d. kerosene

12. Diamond is not a good conductor of electricity because

1. It is very hard

2. Its structure is very compact

3. It is not soluble in water

4. It has no free electrons to conduct electric current.

Ans:  d.  It has no free electrons to conduct electric current.

13. Alcohol can be produced by the hydration of

1. Alkenes

2. Alkynes

3. Alkynes

4. Acids

Ans: a. Alkenes

14. The IUPAC name of $C{{H}_{3}}CHO$ is

1. Acetaldehyde

2. Formaldehyde

3. Methyl formaldehyde

4. Ethanol

Ans: d. Ethanol

15. IUPAC name of the first member of the homologous series of ketones is

1. Ethanone

2. Methanone

3. Propanone

4. Butanone

Ans: c. Propanone

16. An unknown compound has the smell of vinegar. Identify it

Ans: Acetic acid or Ethanoic acid that comprises  $3-9\%$ of the vinegar.

17. Out of butter and groundnut oil which is unsaturated in nature?

Ans: Groundnut oil

18. Which has triple bond,${{C}_{2}}{{H}_{4}},{{C}_{3}}{{H}_{4}},{{C}_{3}}{{H}_{6}}$ 

Ans: ${{C}_{3}}{{H}_{4}}$ 

19. Which substance is added for the denaturation of ethyl alcohol

Ans:  Methyl Alcohol

20. Which ions are responsible for making water hard?

Ans: $C{{a}^{2+}}$ and $M{{g}^{2+}}$ 

21. Ethane, with the molecular formula has

1. \[\mathbf{6}\]  covalent bonds

2. \[\mathbf{7}\] covalent bonds

3. $8$ covalent bonds

4. \[\mathbf{9}\] covalent bonds

Ans: b. $7$  covalent bonds

22. Butanone is a four-carbon compound with the functional group

1. carboxylic acid

2. aldehyde

3. ketone

4. alcohol

Ans: c. Ketone

23. While cooking, if the bottom of the vessels is getting blackened on the outside, it means that

1. The fuel is not cooked completely

2. The fuel is not burning completely

3. The fuel is wet

4. The is burning completely

Ans: b. The fuel is not burning completely.

24. Which of the following hydrocarbons undergo additional reactions?

   ${{C}_{2}}{{H}_{6}},{{C}_{3}}{{H}_{8}},{{C}_{3}}{{H}_{6}},{{C}_{2}}{{H}_{2}}\;and\;C{{H}_{4}}$ 

Ans: ${{C}_{3}}{{H}_{6}}\;and\;{{C}_{2}}{{H}_{2}}$ will undergo addition reactions.

Short Answer Questions                                                                               (2Marks)

1. Name the following compounds 

Ans: Methanol

2. \[C{{H}_{3}}-C{{H}_{2}}-Cl\] 

Ans: Chloroethane

2. Define Soaps?

Ans: A substance used with water for washing and cleaning, made of a compound of natural oils or fats with sodium hydroxide or another strong alkali. These are represented by \[RCOONa\] or \[RCOOR\] .

3. Name the second member of the alkynes family. Give its structure?

Ans: The second member of the alkyne family is propyne. The structural formula is  $C{{H}_{3}}-C\equiv CH$ .

4. Give a chemical test to distinguish between Ethane and Ethene .

Ans:  Take ethane and ethene in two separate test tubes and dissolve them in carbon tetrachloride solution. Pass bromine gas into the two test tubes. If the colour of bromine gas is discharged and decolorizes the yellow colour then that gas is ethene and if the colour of gas remains the same, then that test tube contains ethane gas. 

5. Write the structures of

i. Ethanoic acid

Ans:

ii. Hexanal

Ans: 

6. Name the following compounds

1. $C{{H}_{3}}-\overset{H}{\mathop{C}}\,=0$ 

Ans: Ethanal

2. $C{{H}_{3}}-C{{H}_{2}}-OH$ 

Ans: Ethanol

7. Which organic compound is added to make ethanol unfit for drinking purposes? What is the name of the mixture formed?

Ans: Methanol is highly poisonous and is added in small amounts to ethanol in order to make it unfit for drinking purposes. This mixture is called methylated spirit or denatured alcohol. 

8. Write a test to identify the presence of Ethanoic acid?

Ans: Dip a strip of blue litmus paper in the solution of Ethanoic acid. Its colour changes to red and Ethanoic acid gives a sweet-smelling compound called ester when treated with Ethanol

9. What are the properties of carbon that lead to the huge number of carbon compounds we see around us?

Ans: The two properties of carbon that lead to the huge number of carbon compounds are Catenation and Tetravalency . The self-linking property is called catenation. As Carbon is tetravalent it can readily unite with atoms like hydrogen, oxygen etc by sharing electrons. 

10. Name the following compound.

1. $C{{H}_{3}}-C{{H}_{2}}-Br$ 

Ans: Bromoethane

2. $C{{H}_{3}}-C{{H}_{2}}-C{{H}_{2}}-C\equiv CH$ 

      Ans:  Hex -1- yne

11. Why conversion of ethanol into ethanoic acid is an oxidation reaction?

Ans: Ethanoic acid has one or more ${{O}_{2}}$ atoms and two hydrogen atoms less than ethanol. Loss of hydrogen is known as oxidation and gain of oxygen is known as reduction. Therefore it is an oxidation reaction.

12. A mixture of ethyne and oxygen is used for welding. Can you justify why a mixture of ethyne and air is not used?

Ans: When ethyne is burnt in oxygen, it gives a clean flame with high temperature because of the complete combustion of ethyne. Hence, this oxyacetylene flame is used for welding, and it is not possible to attain a high temperature with air. Air contains a mixture of nitrogen and oxygen. As nitrogen is more in the amount it does not support combustion. Because of this mixture of ethyne and air is not used for welding.

13. Why are carbon and its compounds used as fuels in most cases?

Ans: Carbon compounds are used as fuel because they burn with a clean flame and no smoke is produced which is highly exothermic. Carbon compounds have higher maximum ignition temperature and their combustion can be restrained. Hence, carbon and its compounds are a great source of fuel. 

14. A compound X has the molecular formula ${{C}_{3}}{{H}_{6}}O$  with structural formula $C{{H}_{3}}C{{H}_{2}}CHO$. Give its IUPAC name. Can another compound have the same molecular formula? Give the structure and IUPAC name of that compound also.

Ans: The IUPAC name of X is propanol.

Another similar compound is Y is.

X and Y are related to each other as functional isomers.

15. Why CHO group cannot be present in the middle of the carbon atom chain?

Ans: The terminal functional group is the CHO group and as three valencies of the C-atom are already satisfied; this group cannot be present in the middle of the chain.

16. Two carbon atoms cannot be linked to each other by more than three covalent bonds. Why?

Ans: There is a single bond between the two carbon atoms and both share their one atom therefore for completing its shell it needs to combine with three atoms of carbon or other elements. Therefore, it cannot be linked to more than three covalent bonds since its shell will be completed to become stable

17. What would be the electron dot structure of carbon dioxide which has the formula of?

Ans: $O=C=O$ 

18. What would be the electron dot structure of a molecule of sulphur which is made up of eight atoms of sulphur?

Ans:  Sulphur is a chemical element with the symbol S

19. How would you name the following compounds?

i. $C{{H}_{3}}-C{{H}_{2}}-Br$ 

Ans: Bromomethane

ii. \[H-\overset{\begin{smallmatrix} H \\ | \end{smallmatrix}}{\mathop{C}}\,=O\]

Ans:Methanal

iii. \[H-\underset{\begin{smallmatrix} | \\ H \end{smallmatrix}}{\overset{\begin{smallmatrix} H \\ | \end{smallmatrix}}{\mathop{C}}}\,-\underset{\begin{smallmatrix} | \\ H \end{smallmatrix}}{\overset{\begin{smallmatrix} H \\ | \end{smallmatrix}}{\mathop{C}}}\,-\underset{\begin{smallmatrix} | \\ H \end{smallmatrix}}{\overset{\begin{smallmatrix} H \\ | \end{smallmatrix}}{\mathop{C}}}\,-\underset{\begin{smallmatrix} | \\ H \end{smallmatrix}}{\overset{\begin{smallmatrix} H \\ | \end{smallmatrix}}{\mathop{C}}}\,-C\equiv C-H\]

Ans: Hexyne

20. What are two properties of carbon that lead to the huge number of carbon compounds we see around us?

Ans: The two properties are:

(a) catenation: The ability to form a covalent bond by combining with other carbon

(b) Tetravalancy of carbon.

21. Would you be able to check if water is hard by using a detergent?

Ans: No, we would not be able to check if water is hard by using a detergent.

22. People use a variety of methods to wash clothes. Usually, after adding the soap, they beat the clothes on stone, or beat it with a paddle, scrub with a brush or the mixture is agitated in a washing machine. Why is agitation necessary to get clean clothes?

Ans: Soap lowers the surface tension of water. The long chain non-ionic hydrocarbon group in soap gets attached to the oil or grease droplets and loosens them from the fibres of cloth along with the dirt. However, this loosening is insufficient to remove the grease with dirt completely. Hence the clothes are agitated to remove the grease droplets completely.

23. Explain the nature of the covalent bond using the bond formation in $C{{H}_{3}}Cl$ .

Ans: Covalent bond is formed by sharing of electrons between two atoms. It is non- ionic in nature.

$\quad\quad\quad H$

$\quad\quad\quad \times \quad\quad\quad\quad\quad\quad\quad\quad H$

$\quad\quad\quad\times \quad\quad\quad\quad\quad\quad\quad\quad |$

$H\times \times \;C \times\times \;Cl\longrightarrow H-C-Cl$

$\quad\quad\quad\times \quad\quad\quad\quad\quad\quad\quad\quad |$

$\quad\quad\quad \times \quad\quad\quad\quad\quad\quad\quad\quad H$

$\quad\quad\quad H$

24. Give a test that can be used to differentiate chemically between butter and cooking oil?

Ans: Butter and cooking oil can be differentiated using a bromine water test. Cooking oil will decolourize the red colour of bromine water on shaking and butter will not decolourize.

25. A compound  ‘X’  has a molecular formula. It undergoes substitution reaction readily than an addition reaction. It burns with a blue flame and is present in LPG. Identify ‘X’  and give the balanced equation for its combustion and substitution reaction in presence of sunlight.

Ans: ${{C}_{4}}{{H}_{10}}+\dfrac{13}{2}{{O}_{2}}\to 4C{{O}_{2}}+5{{H}_{2}}O$ 

‘X’

${{C}_{4}}{{H}_{10}}+C{{l}_{2}}\to {{C}_{4}}{{H}_{9}}Cl+HCl$ 

26. ‘A’ compound works well with hard water. It is used for making shampoos & products for cleaning clothes. A is not $100\%$ biodegradable and causes water pollution. ‘B’ does not work well with hard water. It is $100\%$ biodegradable and does not create water pollution. Identify A & B.

Ans: A is the detergent & B is the soap.

27. An organic compound P with molecular formula ${{C}_{2}}{{H}_{6}}O$ is an active ingredient of all alcoholic drinks. It is also used in medicines such as tincture iodine, cough syrups. Identify ‘P’. Drop small pieces of sodium into the test tube containing ‘P’. A new compound ‘Q’ is formed with the evaluation of colourless and odourless gas Name the gas evolved and compound ‘Q’ write the chemical reaction.

Ans:  $2Na+2C{{H}_{3}}C{{H}_{2}}OH\to 2C{{H}_{3}}C{{H}_{2}}{{O}^{-}}N{{a}^{+}}+{{H}_{2}}$ 

Short Answer Questions                                                                             (3 Marks)

1. Complete the following reaction

i. ${{H}_{2}}C=C{{H}_{2}}+{{H}_{2}}O\xrightarrow{{{H}_{2}}S{{O}_{4}}}$

Ans:  ${{H}_{2}}C=C{{H}_{2}}+{{H}_{2}}O\xrightarrow{{{H}_{2}}S{{O}_{4}}}C{{H}_{3}}-C{{H}_{2}}-OH$ 

ii. $HC\equiv CH+B{{r}_{2}}\to $ 

Ans:  \[HC\equiv CH+B{{r}_{2}}\to H-\underset{\begin{smallmatrix} | \\ Br \end{smallmatrix}}{\overset{\begin{smallmatrix} Br \\ | \end{smallmatrix}}{\mathop{C}}}\,-\underset{\begin{smallmatrix} | \\ Br \end{smallmatrix}}{\overset{\begin{smallmatrix} Br \\ | \end{smallmatrix}}{\mathop{C}}}\,-H\]

iii. ${{C}_{2}}{{H}_{5}}OH+Na\to $ 

Ans: $2{{C}_{2}}{{H}_{5}}OH+Na\to 2{{C}_{2}}{{H}_{5}}ONa+{{H}_{2}}$ 

2. What is the role of concentrated sulphuric acid in the esterification reaction?

Ans: In the esterification reaction carboxylic acid reacts with alcohol to form an ester and water reacts in the presence of concentrated sulphuric acid. Concentrated sulphuric acid is used as a catalyst. This reaction is reversible and this reverse reaction is called ester hydrolysis. Concentrated sulphuric acid removes water from the reaction mixture as it is a strong dehydrating agent. As a result, the reaction takes place only in the forward direction to form an ester.

$RCOOH+ROH\xrightarrow{conc{{H}_{2}}S{{o}_{4}}}RCOOR+{{H}_{2}}O$ 

Acid         Alcohol                 Ester

3. What will be the formula and electron dot structure of cyclopentane?

Ans: Cyclopentane is a cyclic compound with a formula ${{C}_{5}}{{H}_{12}}$ . The structure of the compound is represented as

4. Draw the structures of the following compounds

1. Ethanoic acid

2. Bromopentane

3. Butanone

Ans: 

1. Ethanoic acid

$H-\underset{H}{\overset{H}{C}}-\overset{O}{\overset{||}{C}}-OH$

Ethanoicacid 

2. Bromopentane

$C{{H}_{3}}-C{{H}_{2}}-C{{H}_{2}}-C{{H}_{2}}-C{{H}_{2}}-B{{r}}$ Bromopentane 

3. Butanone

$H_3C-\overset{O}{\overset{||}{C}}-CH_2-CH_3$ Butanone 

5. Give names of the following

1. An aldehyde derived from ethane

Ans:Ethane

      $C{{H}_{3}}CHO$ 

2. Ketone derived from butane

1. Ans: Butanone

     $C{{H}_{3}}COC{{H}_{2}}C{{H}_{3}}$ 

3. The compound obtained by the oxidation of ethanol by chromic anhydride

            Ans: Ethanol

$C{{H}_{3}}CHO$ 

6. What is meant by denatured alcohol? What is the need to denature alcohol?

Ans: Ethyl alcohol which contains a small amount of methyl alcohol or copper sulphate is called denatured alcohol. The purpose of denaturing the alcohol is to make it unfit for drinking purposes. Denatured alcohol is also used for industrial purposes.

7. Write chemical equations of the reactions of ethanoic acid with

1. Sodium

            Ans: $ 2C{{H}_{3}}COOH+2Na\to 2C{{H}_{3}}COONa+{{H}_{2}} $

            $ (Sod.Ethanoate) $

2. Sodium carbonate

Ans: $ 2C{{H}_{3}}COOH+N{{a}_{2}}C{{O}_{3}}\to 2C{{H}_{3}}COONa+C{{O}_{2}}+{{H}_{2}}O $

            $ (Sod.Ethanoate)

3. Ethanol in the presence of conc.${{H}_{2}}S{{o}_{4}}$ 

Ans: $ C{{H}_{3}}COOH+{{C}_{2}}{{H}_{5}}OH\xrightarrow{conc.{{H}_{2}}S{{o}_{4}}}C{{H}_{3}}COOC{}_{2}{{H}_{5}} $

$ (Ethyl.ethanoate) $

8. Complete the reaction and names of the products formed

i. \[C{{H}_{3}}COOH+NaOH\xrightarrow{(Heat)}\]

Ans: $ C{{H}_{3}}COOH+NaOH\xrightarrow{(Heat)}C{{H}_{3}}COONa+{{H}_{2}}O $

$ (Sod.Ethanoate) $

ii. ${{C}_{2}}{{H}_{5}}OH+{{O}_{2}}\dfrac{alkaline}{KMnOH}$

Ans: $ {{C}_{2}}{{H}_{5}}OH+{{O}_{2}}\dfrac{alkaline}{KMnOH}C{{H}_{3}}COOH+{{H}_{2}} $

$ (EthanoicAcid) $

iii. $C{{H}_{3}}COOH+{{C}_{2}}{{H}_{5}}OH\xrightarrow{(Conc.{{H}_{2}}Sol)}$

Ans: $ C{{H}_{3}}COOH+{{C}_{2}}{{H}_{5}}OH\xrightarrow{(Conc.{{H}_{2}}Sol)}C{{H}_{3}}COO{{C}_{2}}{{H}_{5}}+{{H}_{2}}O $

$ (EthylEthanoate) $

9. What is a homologous series? State any two characteristics of homologous series?

Ans: A homologous series is a series of hydrocarbons that have similar chemical properties and they share the same general formula. They are organic compounds having similar structures and functional groups. A particular series differ in their molecular formula by the group. Characteristics of homologous series are:- Same functional group and same chemical properties. 

10. Give the structural formulas for

1. Methyl Ethanoate

2. Ethyl Ethanoate

Write two uses of Ester?

Ans: 

i. Methyl Ethanoate

\[H-\overset{\begin{smallmatrix} o \\ || \end{smallmatrix}}{\mathop{C}}\,-OC{{H}_{3}}\]

ii. Ethyl Ethanoate

\[C{{H}_{3}}COO{{C}_{2}}{{H}_{5}}\]

Uses of esters:

a) Esters that have fragrant odours are used as a constituent of perfumes, essential oils, food flavourings, cosmetics, etc.

b) It is used as an organic solvent.

c) Esters of glycerol known as triglycerides are used in the manufacture of soaps.

d) Natural esters are found in pheromones.

11. What are enzymes? Name the enzymes required for the fermentation of sugarcane to ethanol?

Ans: An enzyme is a protein molecule in cells that works as a biological catalyst. In the process of fermentation of sugar into ethanol, two enzymes are used.

${{C}_{12}}{{H}_{22}}{{O}_{11}}+{{H}_{2}}O\xrightarrow{(Invertase)}{{C}_{6}}{{H}_{12}}{{O}_{6}}+{{C}_{6}}{{H}_{12}}{{O}_{6}}$ 

Sugar glucose fructose

${{C}_{6}}{{H}_{12}}{{O}_{6}}\xrightarrow{(Zymase)}2{{C}_{2}}{{H}_{5}}OH+2C{{O}_{2}}$ 

Glucose and Fructose

12. The formula of an ester is ${{C}_{3}}{{H}_{7}}COO{{C}_{2}}{{H}_{5}}$  .Write the formulae of the acid and alcohol from which the ester is prepared.

Ans: The molecular formula of acid is${{C}_{3}}{{H}_{7}}COOH$  (Butanoic acid) and for alcohol is ${{C}_{2}}{{H}_{5}}OH$  (Ethyl alcohol)

${{C}_{3}}{{H}_{7}}COOH+{{C}_{2}}{{H}_{5}}OH\to {{C}_{3}}{{H}_{7}}COO{{C}_{2}}{{H}_{5}}+{{H}_{2}}O$ 

13. Write three differences between ethanol and ethanoic acid on the basis of chemical properties?

Ans: 

i. Add a small amount of $NaHC{{O}_{3}}$ to ethanoic acid $C{{O}_{2}}$ gas is evolved with brisk effervescence and such reaction doesn’t take place in case of ethanol

$C{{H}_{3}}COOH+NaHC{{O}_{3}}\to C{{H}_{3}}COONa+C{{O}_{2}}+{{H}_{2}}O$ 

ii. Ethanol is neutral so does not bring any change in the colour of litmus paper but ethanoic acid is acidic and changes the colour of a blue litmus strip to red when dipped in it.

iii. Ethanoic acid reacts with $NaOH$ and $KOH$ to form salt and water whereas ethanol does not react.

$C{{H}_{3}}COOH+NaHC{{O}_{3}}\to C{{H}_{3}}COONa+{{H}_{2}}O$ 

$C{{H}_{3}}COOH+KOH\to C{{H}_{3}}COOK+{{H}_{2}}O$ 

14. Given a chemical test to distinguish between

i. Ethene and ethane

Ans: Ethene decolorizes the yellow colour of bromine while ethane does not.

ii. Ethanol and ethanoic acid

Ans: Ethanoic acid gives a brisk effervescence with sodium hydrogen carbonate while ethanol does not.

iii. Soaps and Detergents

Ans: Soaps form curdy white precipitate or scum with hard water while detergents do not form any precipitate.

15. Name the functional groups present in the following compounds?

i. $C{{H}_{3}}-C{{H}_{2}}-C{{H}_{2}}-OH$ 

Ans: $-OH(ol)$ 

ii. $C{{H}_{3}}-C{{H}_{2}}-C{{H}_{2}}-COOH$ 

Ans: $-COOH(oic\_acid)$

iii. $C{{H}_{3}}-C{{H}_{2}}-CHO$ 

Ans:  $-CHO(al)$ 

16. What are esters? Write an equation to show the formation of an ester?

Ans: Esters any of a class of organic compounds that react with water to produce alcohols and organic or inorganic acids. They are pleasant smelling compounds and are commonly used as flavouring agents. Monocarboxylic acids react with alcohol to form esters and water. This reaction is called esterification

Methyl Ethanoate (Ester)

$C{{H}_{3}}COOH+C{{H}_{3}}OH\xrightarrow{(Conc.{{H}_{2}}SOH)}C{{H}_{3}}COOC{{H}_{3}}+{{H}_{2}}O$ 

Ethyl Ethanoate (Ester)

$C{{H}_{3}}COOH+{{C}_{2}}{{H}_{5}}OH\xrightarrow{(Conc.{{H}_{2}}S{{O}_{4}})}C{{H}_{3}}COO{{C}_{2}}{{H}_{5}}+{{H}_{2}}O$ 

17. What will be the formula and electron dot structure for cyclopentane?

Ans: Formula of cyclopentane is ${{C}_{5}}{{H}_{10}}$. The electron dot structure cyclopentane is :

18. How many structural isomers can you draw for pentane?

Ans: The isomers are as under : 

\[ H-\underset{\begin{smallmatrix} | \\ H \\ \end{smallmatrix}}{\overset{\begin{smallmatrix} H \\ | \end{smallmatrix}}{\mathop C}}\,-\underset{\begin{smallmatrix} | \\ H \end{smallmatrix}}{\overset{\begin{smallmatrix} H \\ | \end{smallmatrix}}{\mathop C}}\,-\underset{\begin{smallmatrix} | \\ H \end{smallmatrix}}{\overset{\begin{smallmatrix} H \\ | \end{smallmatrix}}{\mathop C}}\,-\underset{\begin{smallmatrix} | \\ H \end{smallmatrix}}{\overset{\begin{smallmatrix} H \\ | \end{smallmatrix}}{\mathop C}}\,-\underset{\begin{smallmatrix} | \\ H \end{smallmatrix}}{\overset{\begin{smallmatrix} H \\ | \end{smallmatrix}}{\mathop C}}\,-H \]

1. n - pentane

2. iso-pentane

19. What is a homologous series? Explain with an example.

Ans:  A sequence of compounds with the same functional group substitutes for hydrogen in a carbon chain is called homologous series. The difference between the formulae of any two successive members is $-C{{H}_{2}}$  and the difference between the molecular formula is\[14\text{ }u\] .

20. How can ethanol and Ethanoic acid be differentiated on the basis of their physical and chemical properties?

Ans:

1. On the basis of physical properties:

• The melting and boiling points of ethanol is $156K$and $351K$ 

• The melting and boiling point of Ethanoic acid is $290K$and $391K$.

2. On the chemical properties: 

• Ethanoic acid reacts with sodium hydrogen carbonate liberating carbon dioxide 

• ethanol does not react with sodium hydrogen carbonate liberating carbon dioxide.

21. Why are carbon and its compounds used as fuels for most applications?

Ans: Carbon burns with a clean flame and no smoke is produced on combustion it gives carbon dioxide and water. This reaction involves the evolution of heat and light. The same takes place for compounds of carbon. That is the reason why carbon and its compounds are used as fuel for most applications.

22. Explain the formation of scum when hard water is treated with soap.

Ans: When soap is dissolved in hard water it reacts with calcium and magnesium ions that are present there and forms calcium and magnesium salt of fatty acid which reacts with soap to form scum. For example, calcium chloride reacts with soap to form scum. 

\[Sodium~stearate\text{ }+\text{ }Calcium\text{ }chloride\to sodium~chloride\text{ }+\text{ }Calcium\text{ }stearate\left( scum \right)\]

23. What change will you observe if you test soap with litmus paper (red and blue)?

Ans: Soap is a sodium or potassium salt of fatty acid. Soap molecules have two ends. Soap is obtained when caustic soda is treated with oil. Sodium stearate is thus a salt of a weak acid and a strong base. As its water solution is slightly alkaline it will turn red litmus red.

24. What is hydrogenation? What is its industrial application?

Ans: The process of adding unsaturated hydrocarbons and hydrogen in presence of catalysts such as palladium or nickel to give saturated hydrocarbons is called hydrogenation. It is commercially used for converting vegetable oils to vanaspati ghee in presence of nickel as a catalyst.

25. Explain the mechanism of the cleaning action of soap.

Ans: Soaps are sodium or potassium salt of fatty acids. Soap molecules have two ends. One end is hydrophilic and another end is hydrophobic. Two molecular ends behave differently. This ionic end is hydrophilic and is oriented towards the water. The other hydrocarbon end is hydrophobic and is oriented towards dirt which is oily in nature. A micelle formation around the oily dirt takes place. The cleaning of clothes etc takes place when flushed with excess water; the micelle containing the dirt is removed.

26. An organic compound X with a molecular formula C undergoes oxidation within the presence of alkaline $KMn{{O}_{4}}$ to form a compound I X on heating in presence of Cone. $11$ At $443$ K gives Z. which on reaction with \[\mathbf{112}\] cm presence of \[\mathbf{11}\] gives back ‘X‘‘Z’ reacts with Br (aq) and decolorizes it. Identify X, Y, & Z and write the reactions involved.

Ans: $C{{H}_{3}}-C{{H}_{2OH}}\xrightarrow[{{K}_{2}}C{{r}_{2}}{{O}_{4}}+Heat]{AlkalineKMn{{O}_{4+Heat}}}C{{H}_{3}}COOH$ 

                 X                                                    Y

 $C{{H}_{3}}-C{{H}_{2}}OH\xrightarrow[{{H}_{2}}S{{O}_{4}}]{HotCOOC}C{{H}_{2}}=C{{H}_{2}}+{{H}_{2}}O$ 

                                                          Z

27. ‘A’ compound works well with hard water. It is used for making shampoos & products for cleaning clothes. A is not 100% biodegradable and causes water pollution. ‘B’ does not work well with hard water. It is 100% biodegradable and does not create water pollution. Identify A & B.

Ans: ‘Y’ will burn with a sooty flame. So it is an unsaturated hydrocarbon.

Propane (X)

Propene (Y)

28. A cyclic compound ‘X’ has molecular formula. It is unsaturated and burns with a sooty flame. Identify ‘X’ and write its structural formula. Will it decolourize bromine water or not and why?

Ans:

It does not decolourize bromine water because it does not undergo additional reactions.

29. An organic compound ‘A’ is a constituent of antifreeze and has the molecular formula${{C}_{2}}{{H}_{6}}O$ . Upon reaction with alkaline $KMn{{O}_{4}}$ the compound ‘A’ is oxidized to another ‘B’ with formula C Identify the compound A’ and ‘B’. Write the chemical equation for the reaction which leads to the formulation of ‘B’

Ans: $C{{H}_{3}}-C{{H}_{2}}OH\xrightarrow[KC{{r}_{2}}{{O}_{7}}+Heat]{AlkalineKMn{{O}_{4}}+Heat}C{{H}_{3}}COOH$ 

                  ‘A’                                                  ‘B’

30. Two compounds ‘X’ and ‘Y’ have the same formula C. One of them reacts with sodium metal to liberate \[\mathbf{112}\]  and CO with NaHCO Second one does not react with Na metal and NaHCO but undergo hydrolysis with NaOH to form a salt of carboxylic acid and compound ‘Z’ which is called wood spirit. Identify ‘X’, ‘Y’, and ‘Z’ and write a chemical equation for the reaction involved.

Ans: $C{{H}_{3}}COOH+NaHC{{O}_{3}}\to C{{H}_{3}}COONa+{{H}_{2}}O+C{{O}_{2}}$ 

                    ‘X’

         $C{{H}_{3}}COOH+Na\to C{{H}_{3}}COONa+{{H}_{2}}$ 

          $HCOO{{H}_{3}}+NaOH\to HCOONa+C{{H}_{3}}OH$ 

                ‘Y’                             ‘Z’

31. A compound ‘X’ with molecular formula C burns with a sooty flame. It decolorizes bromine water. Identify ‘X’ Will it dissolve in water or not? Will it conduct electricity in aq. Solution? Will it have a high melting point or a low melting point?

Ans: As ‘X’ ethane is a covalent compound it will neither dissolve in water nor conduct electricity and it has a low melting point.

Long Answer Questions                                                                               (5 Marks)

1. Define fermentation. Name the enzyme which converts

1. Milk into curd (yoghurt)

2. Cane sugar into glucose and fructose

3. Glucose into ethanol

Ans: The chemical process of preparation of ethyl alcohol from sugar is known as fermentation.

1. Milk into curd (yoghurt): Lactase

2. Cane sugar into glucose and fructose: Invertase

3. Glucose into ethanol: Zymase

2. a. Name the gas that evolved during the fermentation process?

Ans: $C{{O}_{2}}$ Gas is evolved and accompanied by brisk effervescence.

b. What role is played by yeast in the conversion of cane sugar to ethanol?

Ans: Yeast is the source of enzymes invertase and zymase needed for fermentation.

c. How may the following be obtained from pure ethanol? Express$({{C}_{12}}{{H}_{22}}{{O}_{11}})$ chemical reactions by the chemical equations.

1. Sodium ethoxide

Ans: $2{{C}_{2}}{{H}_{5}}OH+2Na\to 2{{C}_{2}}{{H}_{5}}ONa+{{H}_{2}}$

2. Ethyl ethanoate

Ans: $ 2{{C}_{2}}{{H}_{5}}OH+C{{H}_{3}}COOH\xrightarrow{{{H}_{2}}S{{O}_{4}}}C{{H}_{3}}COO{{C}_{2}}{{H}_{5}}+{{H}_{2}}O $

$ (EthylEthanoate) $

3. Ethanal

Ans: ${{C}_{2}}{{H}_{5}}OH+\dfrac{1}{2}{{O}_{2}}\xrightarrow[C{{h}_{3}}COOH]{Cr{{O}_{3}}}C{{H}_{3}}CHO+{{H}_{2}}O$ 

3. An organic compound A is widely used as a preservative in pickles and has a molecular formula. This compound reacts with ethanol to form a sweet-smelling compound B.

1. Identify compound A.

            Ans: Compound A is ethanoic acid $(C{{H}_{3}}COOH)$ 

2. Write the chemical equation for its reaction with ethanol to form compound B.

Ans:  $C{{H}_{3}}COOH+{{C}_{2}}{{H}_{5}}OH\to C{{H}_{3}}COO{{C}_{2}}{{H}_{5}}+{{H}_{2}}O$

3. How can we get compound A back from B?

Ans: Ethanoic acid Ethyl Ethanoate (Ester)

$C{{H}_{3}}COO{{C}_{2}}{{H}_{5}}+{{H}_{2}}O\xrightarrow{{{H}^{+}}}C{{H}_{3}}COOH+{{C}_{2}}{{H}_{5}}OH$

Ethanoic acid

4. Name the process and write the corresponding chemical equation.

Ans: The process is known as ester hydrolysis.

5. Which gas is produced when compound A reacts with washing soda? Write the chemical equation?

Ans: $C{{O}_{2}}$ is produced with effervescence when compound A reacts with washing soda which is chemical $N{{a}_{2}}C{{O}_{3}}$ 

$2C{{H}_{3}}COOH+N{{a}_{2}}C{{O}_{3}}\to 2C{{H}_{3}}COONa+{{H}_{2}}O+C{{O}_{2}}$ 

4.  

1. Why does carbon form the largest number of compounds?

Ans: Carbon forms strong bonds with another carbon due to the overlapping of orbitals. Carbon forms a large number of compounds called organic compounds due to which the self-linking property is called catenation.

2. Why some of these are called saturated and other unsaturated compounds?

Ans: Compounds which has only $C-C$ (single bond) present are saturated compounds whose as those compounds which have \[\mathbf{C}=\mathbf{C}\] (double  bond) or  \[\mathbf{C}\equiv \mathbf{C}\]  (triple) bond is present are called unsaturated compounds.

3. Which of these two is more reactive?

Ans:  Saturated compounds are less reactive than unsaturated compounds

4. Write the names of the following compounds

i. $C{{H}_{2}}-C{{H}_{2}}-Br$ 

Ans: Bromoethane

ii. $C{{H}_{3}}-CH-CH-CH-C\equiv C-H$ 

Ans: Hex-1-yne

5. Draw the structure for the following compounds:

i. Ethanoic acid

Ans:

ii. Bromopentane

Ans:

iii. Butanone

Ans:

\[H-\underset{\begin{smallmatrix} | \\ H \end{smallmatrix}}{\overset{\begin{smallmatrix} H \\ | \end{smallmatrix}}{\mathop{C}}}\,-\underset{\begin{smallmatrix} | \\ H \end{smallmatrix}}{\overset{\begin{smallmatrix} H \\ | \end{smallmatrix}}{\mathop{C}}}\,-\overset{\begin{smallmatrix} O \\ || \end{smallmatrix}}{\mathop{C}}\,-\underset{\begin{smallmatrix} | \\ H \end{smallmatrix}}{\overset{\begin{smallmatrix} H \\ | \end{smallmatrix}}{\mathop{C}}}\,-H\]

iv. Hexanal

Ans:

\[H-\underset{\begin{smallmatrix} | \\ H \end{smallmatrix}}{\overset{\begin{smallmatrix} H \\ | \end{smallmatrix}}{\mathop{C}}}\,-\underset{\begin{smallmatrix} | \\ H \end{smallmatrix}}{\overset{\begin{smallmatrix} H \\ | \end{smallmatrix}}{\mathop{C}}}\,-\underset{\begin{smallmatrix} | \\ H \end{smallmatrix}}{\overset{\begin{smallmatrix} H \\ | \end{smallmatrix}}{\mathop{C}}}\,-\underset{\begin{smallmatrix} | \\ H \end{smallmatrix}}{\overset{\begin{smallmatrix} H \\ | \end{smallmatrix}}{\mathop{C}}}\,-\overset{\begin{smallmatrix} H \\ | \end{smallmatrix}}{\mathop{C}}\,=O\] 

6. Draw the electron dot structure for

1. Ethanoic acid

Ans:

2. ${{H}_{2}}S$ 

Ans:

3. Propanone 

Ans:

4. ${{F}_{2}}$ 

Ans:

7. Why does micelle formation take place when soap is added to water? Will a micelle be formed in other solvents such as ethanol also?

Ans: Soap molecules have two ends. One end is hydrophilic and another end is hydrophobic and the ionic end is hydrophilic. Soaps dissolve in water while the hydrogen chain is hydrophobic, it dissolves in hydrocarbon. The hydrocarbon chains are oriented towards the oil droplet and the ionic ends are oriented towards the water. In ethanol Micelles, the formation will not take place.

8. An organic compound ‘A’ is widely used as a preservative in pickles and has a molecular formula C. This compound reacts with ethanol to form a sweet-smelling compound ‘B’.

i. Identify the compound ‘A’

Ans: Ethanoic acid, $C{{H}_{3}}COOH$ 

ii. Write the chemical equation for its reaction with ethanol to form compound ‘B’.

Ans: 

iii. How can we get compound ‘A’ back from ‘B’?

Ans: Esters react with the acid or a base to give back the alcohol and carboxylic acid.

iv. Name the process and write the corresponding chemical equation.

Ans: Saponification

$C{{H}_{3}}COO{{C}_{2}}{{H}_{5}}\xrightarrow{NaOH}{{C}_{2}}{{H}_{5}}OH+C{{H}_{3}}COOH$

v. Which gas is produced when compound ‘A’ reacts with washing soda? Write the chemical equation.

Ans: $C{{O}_{2}}$ gas is evolved

\[2C{{H}_{3}}COOH+N{{a}_{2}}C{{O}_{3}}\to 2C{{H}_{3}}COONa+{{H}_{2}}O+C{{O}_{2}}\] 

Solved Examples

1. Explain why the chemical reaction of the conversion of ethanol into ethanoic acid is an oxidation reaction?

Answer. Ethanoic acid has one O2, atom more and two hydrogen atoms less than ethanol. Also, loss of hydrogen is known as oxidation, and gain of oxygen is known as oxidation. So, we can say that the chemical reaction of the conversion of ethanol into ethanoic acid is an oxidation reaction.

2. The molecular formula of X is C3H6O, and its structural formula is CH3CH2CHO. State its IUPAC name. Give an example of another compound that has the same molecular formula? Give the IUPAC name of that compound also. 

Answer. Compound X is Propanal. Another similar compound is Propanone. They are related to each other as functional isomers.

3. List the properties of carbon responsible for the vast number of its compounds around us?

Answer. 

(i) The Self linking property of carbon atom called catenation.

(ii) Carbon is tetravalent and can unite with atoms like hydrogen, oxygen, etc. by covalent bond formation.

4. The mixture of ethyne and oxygen is used for welding instead of a combination of ethyne and air. Explain why?

Answer. Large quantities of heat and light are produced when ethyne is burnt in oxygen. The heat evolved is used for gas welding. Since air contains a mixture of nitrogen and oxygen and nitrogen (in larger quantities) does not support combustion. Hence oxygen is used for the eruption of ethyne.

5. Define fermentation. Name the enzyme which converts:

(a) Milk into curd (yoghurt).

(b) Glucose into ethanol.

Answer. The process of preparation of ethyl alcohol from sugar is known as fermentation.

(a) Lactase converts milk into curd.

(b) Zymase converts glucose into ethanol.

Chapter 4 Science Class 10 Important Questions

Following are some essential points of Chapter 4 Science Class 10:

• Carbon is one of the most versatile elements that are the basis of all living organisms.

• Several compounds can be created using carbon, exhibiting the properties like tetravalency and catenation.

• Carbon forms a covalent bond among itself and other elements like oxygen, hydrogen, nitrogen, sulphur, etc.

• It also creates compounds that contain double and triple bonds among carbon atoms which can be in the form of straight chains, rings, or branched chains.

• The carbon compounds used in our daily life are ethanoic acid, ethanol, etc.

• Both the ends of the soap are present in soap and detergents' action, and it helps in the removal of oily dirt from the cloth.

• Ketones, aldehydes, carboxylic acid, and alcohols are among the functional groups that show characteristic properties to the carbon compounds that contain them.

• Carbons give rise to homologous series of compounds in which the same functional group is attached to the carbon rings of different lengths.

Importance of Questions From Chapter 4 - Carbon and Its Compounds

important questions for Class 10 Science Chapter 4 are required for the following reasons:

• It saves students from mugging up the entire chapter. Important questions consist of essential topics and concepts which are important from an exam point of view. They can study critical issues and gain enough knowledge about the chapter.

• It helps students understand concepts in-depth quickly and reduces cramming up the entire chapter for the students.

• It creates a perfect learning environment for the students to learn and understand topics better and efficiently.

• Students understand essential points and concepts better and easier by solving and practicing questions on crucial topics.

• Students can also analyze the weak parts or topics, in which they need extra care or focus.

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What are the Benefits of Important Questions from Vedantu for Class 10 Chapter 4 Carbon and its Compounds

• Focus on key topics for efficient studying.

• Prepares students for exams and reduces anxiety.

• Reinforces understanding of fundamental concepts.

• Teaches effective time management.

• Enables self-assessment and progress tracking.

• Strategic approach for higher scores.

• Covers a wide range of topics for comprehensive understanding.

• Supports exam preparation and boosts confidence.

Important Related Links for CBSE Class 10 Science