Study Important Questions for Class 10 Science Chapter 4 - Carbon & Its Compounds

 

Study Important Questions for Class 10 Science Chapter 4 - Carbon & 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 is

1. Acetaldehyde

2. Formaldehyde

3. Methyl formaldehyde

4. Ethanol

Ans: d.Ethanol 

6. Dilute alkaline solution is

1. an oxidizing agent

2. a reducing agent

3. a bleaching agent

4. none of these

Ans: a. an oxidizing agent

7. The by-product in the soap industry is

1. Isoprene

2. Ethylene glycol

3. Glycerol

4. Butane

Ans: c. Glycerol

8. The odour of acetic acid resembles that of

1. Rose

2. Burning Plastic

3. Vinegar

4. Kerosene

Ans: d. kerosene

9. 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.

10. Alcohol can be produced by the hydration of

1. Alkenes

2. Alkynes

3. Alkynes

4. Acids

Ans: a. Alkenes

11. The IUPAC name of is

1. Acetaldehyde

2. Formaldehyde

3. Methyl formaldehyde

4. Ethanol

Ans: d. Ethanol

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

1. Ethanone

2. Methanone

3. Propanone

4. Butanone

Ans: c. Propanone

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

Ans: Acetic acid or Ethanoic acid that comprises  of the vinegar.

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

Ans: Groundnut oil

15. Which has triple bond, 

Ans:  

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

Ans:  Methyl Alcohol

17. Which ions are responsible for making water hard?

Ans: and  

18. Ethane, with the molecular formula has

1.   covalent bonds

2. covalent bonds

3. covalent bonds

4. covalent bonds

Ans: b.   covalent bonds

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

1. carboxylic acid

2. aldehyde

3. ketone

4. alcohol

Ans: c. Ketone

20. 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.

21. Which of the following hydrocarbons undergo additional reactions?

    

Ans: will undergo addition reactions.

Short Answer Questions                                                                               (2Marks)

1. 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 or .

2. 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  .

3. 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. 

4. 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. 

5. 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

6. 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. 

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

Ans: Ethanoic acid has one or more 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.

8. 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.

9. 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. 

10. 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.

11. 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 .

12. 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.

13. 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.

14. 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.

15. 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.

16. 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.

17. An organic compound P with molecular formula C2H6O 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.

18. 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.

19. . 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.

20. Give the structural formulas for

1. Methyl Ethanoate

2. Ethyl Ethanoate

Write two uses of Ester?