Ans (a). Compounds of hydrogen and carbon are called hydrocarbons, e.g. methane, ethane, ethene, etc.

Ans (b). All the bonds in saturated hydrocarbons (except in active radicals) are single bonds
but double or triple bond is present in unsaturated hydrocarbons.
 Examples of saturated hydrocarbons: Ethane and methane
 Examples of unsaturated hydrocarbons: Ethyne and ethene 

Ans(c). Functional group – An atom/group of atoms joined in a specific manner which is
responsible for the characteristic chemical properties of the organic compounds. 
Examples are hydroxyl group (–OH), aldehyde group (–CHO), carboxylic group (–COOH) etc. 
 

Addition reaction is used in the conversion of vegetable oils to fats. This is called hydrogenation of oil. Vegetable oils generally have long chains of unsaturated carbons, while animal fats have long chains of saturated carbons. Addition reaction is carried out in the presence of Ni as a catalyst. This reaction can be given by following equation:

It is important to note that unsaturated fat is healthy for eating. But saturated fat is unhealthy.

Ans. Carbon tetrachloride: CCl4

Ans(b). When ester treated with an alkali, the reaction gives ethanol and sodium ethanoate. This reaction is called saponification reaction because this reaction forms the basis of preparation of soap. This can be given by following equation. CH₃COOC₂H₅ +  NaOH → CH₃COONa + C₂H₅OH

Take 1 ml ethanol and 1 ml glacial acetic acid in a test tube. Pour a few drops of conc. sulphuric acid in the test tube.

Gently warm the test tube over a water bath for about 5 minutes. After that, take out the test tube and transfer its contents in a beaker. Take the smell of the content. The sweet smell shows that ester has been made. This reaction can be given by following equation:

C is ethanoic acid. It reacts with sodium to form sodium ethanoate. Hence, compound R is sodium ethanoate or sodium acetate. We know that hydrogen gas burns with a pop sound. This reaction can be given by following equation:

2CH₃COOH  + 2Na → 2CH₃COONa + H₂ 

When ethanoic acid reacts with methanol in the presence of an acid, we get (methyl ethanoate) ester which is a sweet smelling substance. Hence, compound S is methyl ethanoate and A is methanol. This reaction can be given as follows:

CH₃COOH  + CH₃OH  --Acid → CH₃COOH-CH₃ 

When sodium hydroxide is added to ethanoic acid, it gives sodium ethanoate and water.

CH₃COOH  + NaOH  → CH₃COONa  + H₂O 

When methyl ethanoate is treated with NaOH solution, it gives back methanol and sodium ethanoate.

CH₃COO-CH₃ + NaOH  → CH₃OH + CH₃COONa

Compound A is ethanol. When it is heated with concentrated sulphuric acid, we get ethene. So, compound B is ethene. This can be shown by following equation

CH₃CH2OH  ------Conc.H₂SO₄→ CH₂  = CH₂ + H₂O

When ethene is heated in the presence of nickel, we get ethane. This can be shown by following equation.

CH₂  = CH₂  ------Ni→ C₂H₆ (Compound C)

When 1 mole of ethane is burnt, we get 2 moles of carbon dioxide and 3 moles of water; as shown by following equation.

C₂H₆ + 7O₂ → 4CO₂ + 6H₂O

Addition of hydrogen to unsaturated hydrocarbon to obtain a saturated hydrocarbon is called hydrogenation reaction. Hydrogenation is used for converting unsaturated vegetable oil into fat. This can be shown by following equation:

When oxygen is added to alcohol to make carboxylic acid, this is called oxidation reaction. Following is an example of oxidation of alcohol