A compound A (C₂H₄O₂) reacts with Na metal to form a compound ‘B’ and evolves a gas which burns with a pop sound. Compound ‘A’ on treatment with an alcohol ‘C’ in the presence of acid forms a Sweet-smelling compound ‘D’ (C₄H₈O₂). On addition of NaOH to ‘D’ gives back B and C. Identify A, B, C and D write the reactions involved.

OR

a. Explain why carbon forms a covalent bond? Give two reasons for carbon forming a large number of compounds.

b. Explain the formation of ammonia molecule.

The compound A is acetic acid (CH₃COOH) as acetic acid reacts with sodium metal to form sodium ethoxide and the gas liberated is hydrogen gas as hydrogen gas only burns with a pop sound.

Acetic acid reacts with alcohol to form an ester and esters, in general, are sweet smelling compounds.

When sodium hydroxide is added to compound D we get back the original compounds back. The set of reactions is as follows:

Hence the compounds are as follows:

A = Acetic Acid [CH₃COOH]

B = Sodium Ethoxide [CH₃COONa]

C = Ethanol [C₂H₅OH]

D = Ethyl Ethanoate [CH₃COOC₂H₅]

OR

a. Carbon is the first element of group 14 which implies that carbon contains four electrons in the outermost shell.

1. To attain the nearest noble gas configuration, a carbon atom requires four more electrons in its outermost shell.

2. Since a carbon atom has four electrons, each carbon atom cannot donate or accept any electron. Hence to attain stability a carbon atom prefers to share the electrons with other carbon atoms.

3. Carbon atom shows the highest affinity for catenation that is the ability of an atom to form links or bonds with its own type to form a long chain of compounds. Due to the property of catenation, carbon atom forms a large variety of compounds.

4. A carbon atom has four bonds which need to be formed. So, it can form these bonds easily with several other elements leading to the formation of many compounds.

b. The chemical formula of the ammonia molecule is NH3 which means that three hydrogen atoms form a covalent bond with a single nitrogen atom. Ammonia molecule is gaseous in nature.

1. The atomic number of nitrogen is seven which implies that in the outermost shell of nitrogen there are five electrons. To attain the stability of the nearest noble gas configuration, nitrogen atom requires three more electrons.

2. On the other hand, the hydrogen atom requires one electron to attain stable octet. Hence three atoms of hydrogen pair with the three bonds of nitrogen forming three covalent bonds.

3. The ammonia molecule is as follows:

Ammonia molecule is a gas at room temperature.