Chapter 4 – Carbon and Its Compounds

1) Why ethanol conversion to ethanoic acid is considered an oxidation reaction?

Ans – The conversion of ethanol (C₂H₅OH) to ethanoic acid (CH₃COOH) is considered an oxidation reaction because it involves the increase in the oxidation state of carbon atoms within the ethanol molecule.

As we can witness, ethanoic acid has one or more oxygen atoms and 2 H atoms less than ethanol. Since the loss of H atoms is oxidation while the gain of O₂ is reduction, the process here is oxidation.

2) In welding, a mixture of oxygen and ethyne is used. Why is air not used instead?

Ans – In welding, a mixture of oxygen (O₂) and ethyne (acetylene, C₂H₂) is used instead of air because this combination produces a significantly higher flame temperature, which is necessary for effective welding.

The combustion of acetylene with pure oxygen is much more efficient and produces an excessive heat flame (oxyacetylene flame). However, the air contains approximately 21% oxygen and 78% nitrogen. When acetylene is burned in the air, the nitrogen acts as a diluent, reducing the overall temperature of the flame. Hence, the air ethyne mixture is not used.

3) Compound X has the molecular formula C₃H₆O, while a structural formula CH₃CH₂CHO. What is the IUPAC name of it? Can two compounds share the same molecular formula? Give its structural formula and IUPAC name.

Ans – The IUPAC name of X is propanol.

Similar compound with same molecular formula is:

They are related to each other as functional isomers.

4) What does concentrated sulphuric acid do in the esterification reaction?

Ans – In the esterification reaction, concentrated sulphuric acid primarily catalyzes to accelerate the reaction and as a dehydrating agent increases the yield of the ester by removing water from the reaction mixture. This reversible reaction is called ester hydrolysis. But with concentrated sulphuric acid, the reaction only moves forward to form ester.

5) Name the following compounds.

1. An ethane-derived aldehyde
   Ans – Ethane (CH₃CHO)
2. A butane derived from Ketone
   Ans – Butanone (CH₃COCH₂CH₃)
3. A compound derived from ethanol oxidation by chromic anhydride
   Ans – Ethanol (CH₃CHO)

6) What do you understand by esters? Write an equation to show how esters form.

Ans – Esters are a class of organic compounds characterized by the functional group R-COO-R’ which react with water to form alcohols and organic and inorganic acids. They are known for their pleasant, often fruity smells.

Esters are formed through a chemical reaction known as esterification, which involves a carboxylic acid reaction with an alcohol, typically in the presence of an acid catalyst such as concentrated sulfuric acid.

7) Why do fuels for most applications come from carbon and its compounds?

Ans – Carbon-oriented fuels have high energy densities, meaning they contain more energy per unit mass or volume. Also, carbon burns with clean flame producing no smoke & producing carbon dioxide and water on combustion. This makes them efficient energy sources for various applications, from powering vehicles to generating electricity.

8) Describe the mechanism of the cleaning action of soaps.

Ans – Soaps are cleaned by a process called emulsification. During the molecular stage, soaps have molecules with 2 unique variations: a hydrophilic (water-attracting) head & a hydrophobic (water-repelling) tail.

When combined with water, the hydrophilic heads project themselves toward the water while the hydrophobic tails point in the opposite direction. While applying the soap to surfaces containing dirt, grease, or oil, the hydrophobic tails of the soap molecules are attracted to the oily or greasy substances.

These tails cover the dirt elements, creating unique structures called micelles. The hydrophilic heads of the soap molecules are portrayed to face outward, enabling the overall micelle to be submerged in water for rinsing.

9) A is an organic compound having a molecular representation of C also known as a preservative substance for pickled products. A reacts with ethanol and produces B, which has a fruity smell.

a. What is A?

Ans – Ethanoic acid, CH₃COOH

b. Write the chemical reaction for the whole process when A reacts with ethanol to form B

Ans –

c. How can we get A from B?

Ans – After reaction of ester with acid or base, it gives the alcohol and carboxylic acid.

d. What is the process called? Write a chemical reaction for it

Ans – Saponification

e. When A reacts with washing soda, what gas is liberated? Write the chemical reaction for the same.

Ans – CO₂ gas is liberated.
2CH₃COOH + Na₂CO₃ → 2CH₃COONa + H₂O + CO₂