11. Carbon and its Compounds

I. Choose the best answer.

1. The molecular formula of an open – chain organic compound is C3H6. The class of the compound is ______.

(a) alkane        (b) alkene
(c) alkyne        (d) alcohol.

2. The IUPAC name of an organic compound is 3-Methyl butan-1-ol. What type of compound it is?

(a) Aldehyde
(b) Carboxylic acid
(c) Ketone
(d) Alcohol.

3. The secondary suffix used in IUPAC nomenclature of an aldehyde is ______.

(a) – ol             (b) – oic acid
(c) – al             (d) – one.

4. Which of the following pairs can be the successive members of a homologous series?

(a) C3H8 and C4H10
(b) C2H2 and C2H4
(c) CH4 and C3H6
(d) C2H5OH and C4H8OH

5. C2H5OH + 3O2 → 2CO2 + 3H2O is a ______.

(a) Reduction of ethanol
(b) Combustion of ethanol
(c) Oxidation of ethanoic acid
(d) Oxidation of ethanol.

6. Rectified spirit is an aqueous solution which contains about ………… of ethanol.

(a) 95.5%       (b) 15.5%
(c) 55.5%        (d) 45.5%

7. Which of the following are used as anaesthetics?

(a) Carboxylic acids
(b) Ethers
(c) Esters
(d) Aldehydes.

8. TFM in soaps represents ………… content in soap.

(a) mineral       (b) vitamin
(c) fatty acid   (d) carbohydrate

9. Which of the following statements is wrong about detergents?

(a) It is a sodium salt of long – chain fatty acids
(b) It is sodium salts of sulphonic acids
c) The ionic part in a detergent is –SO3–Na+
(d) It is effective even in hard water.

II. Fill in the blanks.

1. An atom or a group of atoms which is responsible for chemical characteristics of an organic compound is called Functional group.

2. The general molecular formula of alkynes is CnH2n-2.

3. In IUPAC name, the carbon skeleton of a compound is represented by Root word.

4. Unsaturated compounds decolourize bromine water.

5. Dehydration of ethanol by concentrated Sulphuric acid forms Ethene.

6. 100% pure ethanol is called Absolute alcohol.

7. Ethanoic acid turns Blue litmus to red.

8. The alkaline hydrolysis of fatty acids is termed as Saponification.

9. Biodegradable detergents are made of Straight chain hydrocarbons.

III. Match the following

i. Functional group –OH

c. Alcohol

ii. Heterocyclic

d. Furan

iii. Unsaturated

e. Ethene

iv. Soap

b. Potassium stearate

v. Carbocyclic

a. Benzene

IV. Assertion and Reason.

Answer the following questions using the data given below:
(i) A and R are correct, R explains the A.
(ii) A is correct, R is wrong.
(iii) A is wrong, R is correct.
(iv) A and R are correct, R doesn’t explain A.

1. Assertion: Detergents are more effective cleansing agents than soaps in hard water.
Reason: Calcium and magnesium salts of detergents are water – soluble.
Answer:
(ii) A is correct, R is wrong.

2. Assertion: Alkanes are saturated hydrocarbons.
Reason: Hydrocarbons consist of covalent bonds.
Answer:
(iv) A and R are correct, R doesn’t explain A.
Alkanes are saturated hydrocarbons due to the presence of single bonds.

V. Short Answer Questions.

1. Name the simplest ketone and give its structural formula.

Simplest ketone contains three carbon atom chain with the molecular formula C3H6O.

2. Classify the following compounds based on the pattern of the carbon chain and give their structural formula:

  1. Propane
  2. Benzene
  3. Cyclobutane
  4. Furan.

Answer:

  1. Propane is an open chain or a cyclic compound because it contains an open chain.
    CH3-CH3-CH3 [Propane].
  2. Benzene is a carbocyclic compound because it contains carbon atoms cyclic ring of 6 atoms.

  3. Cyclobutane is a carbocyclic compound.
  4. Furan is a heterocyclic compound because in the cyclic chain one atom is oxygen atom. HC – CH

3. How is ethanoic acid prepared from ethanol? Give the chemical equation.

Ethanoic acid can be prepared by oxidation of ethanol in the presence of alkaline potassium permanganate of acidified potassium dichromate.


4. How do detergents cause water pollution? Suggest remedial measures to prevent this pollution?

(i) Some detergents having a branched hydrocarbon chain are not fully biodegradable by microorganism present in water and they cause water pollution.
(ii) Remedial Action: We have to use biodegradable detergents which have linear hydrocarbon chains.

5. Differentiate soaps and detergents.
Answer:

Soaps

Detergents

1. It is a sodium salt of long – chain fatty acids.

1. It is a sodium salt of sulphonic acids.

2. Its effectiveness is reduced when used in hard water.

2. It is effective even in hard water.

3. Soaps are biodegradable.

3. Most of the detergents are non-biodegradable.

VI. Long Answer Questions.

1. What is called a homologous series? Give any three of its characteristics?

A homologous series is a group or a class of organic compounds having same general formula and similar chemical properties in which the successive members differ by a -CH2 group.
Characteristics of homologous series:

  1. Each member of the series differs from the preceeding or succeeding member by one methylene group (-CH2) and hence by a molecular mass of 14 amu.
  2. All members of a homologous series contain the same elements and functional group.
  3. They are represented by a general molecular formula. Eg: Alkanes, C2H2n+2.
  4. The members in each homologous series show a regular gradation in their physical properties with respect to their increase in molecular mass.
  5. Chemical properties of the members of a homologous series are similar.
  6. All the members can be prepared by a common method.

2. Arrive at, systematically, the IUPAC name of the compound: CH3 – CH2 – CH2 – OH.

·         Step 1: The parent chain consists of 4 carbon atoms. The root word is ‘but’.

  • Step 2: All are single bonds between the carbon atoms of the chain. So the primary suffix is ‘ane’.
  • Step 3: Since the compound contains the -OH group, it is an alcohol. The secondary suffix is ‘ol’.
    But + ane + ol = Butan-ol = Butanol.

3. How is ethanol manufactured from sugarcane?

Fermentation method can be used to obtain ethanol from sugarcane. Actually, in industries, C2H5OH is prepared by the fermentation of molasses, which is a by – product obtained during the manufacture of sugar from sugarcane.
It is converted into ethanol by following steps:

  • Dilution of molasses
  • Addition of nitrogen source
  • Addition of yeast
  • Distillation of wash.

Chemical Reductions:


4. Give the balanced chemical equation of the follows ing reactions:
(i) Neutralization of NaOH with ethanoic acid.
(ii) Evolution of carbon dioxide by the action of ethanoic acid with NaHCO3
(iii) Oxidation of ethanol by acidified potassium dichromate.
(iv) Combustion of ethanol.
Answer:
i) Neutralization of NaOH with ethanoic acid. Ethanoic acid reacts with sodium hydroxide to form sodium ethanoate and water.

ii) Evolution of carbon dioxide by the action of ethanoic acid with NaHCO3. Ethanoic acid reacts with sodium bicarbonate to give salt, water and carbon dioxide gas.

iii) Oxidation of ethanol by acidified potassium dichromate. Ethanol is oxidised to ethanoic acid with alkaline KMnO4 or acidified K2Cr2O7

iv) Combustion of ethanol. Ethanol is highly inflammable liquid. It burns with oxygen to form carbon dioxide and water.

5. Explain the mechanism of cleansing action of soap.

(i) A soap molecule contains two chemically distinct parts that interact differently with water. It has one polar end, which is a short head with a carboxylate group (-COONa) and one non-polar end having the long tail made of the hydrocarbon chain.

(ii) The polar end is hydrophilic (Water loving) in nature and this end is attracted towards water. The non-polar end is hydrophobic (Water hating) in nature and it is attracted towards dirt or oil on the cloth, but not attracted towards water. Thus, the hydrophobic part of the soap molecule traps the dirt and the hydrophilic part makes the entire molecule soluble in water.

(iii) When a soap or detergent is dissolved in water, the molecules join together as clusters called ‘micelles’. Their long hydrocarbon chains attach themselves to the oil and dirt. The dirt is thus surrounded by the non-polar end of the soap molecules. The charged carboxylate end of the soap molecules makes the micelles soluble in water. Thus, the dirt is washed away with the soap.

VII. HOT Questions.

1. The molecular formula of an alcohol is C4H10O. The locant number of its -OH group is 2.
(i) Draw its structural formula.
(ii) Give its IUPAC name.
(iii) Is it saturated or unsaturated?
Answer:



the group is placed in the secondary carbon atom.

(ii) Butan-2-ol

(iii) In butan-2-al all bonds are single bonds. So, this is a saturated compound.

2. An organic compound ‘A’ is widely used as a preservative and has the molecular formula C2H4O2. This compound reacts with ethanol to form a sweet – smelling compound ‘B’.

  1. Identify the compound ‘A’.
  2. Write the chemical equation for its reaction with ethanol to form compound ‘B’.
  3. Name the process.

Answer:

  1. Acetic acid (CH3COOH) is widely used as a preservative.
  2. CH3COOH reacts with ethanol to form fruity smell ester, this reaction is known as an esterification reaction.
  3. Esterification process.