Question: 72. Match List I with List II.
| List-I (Molecule) | List-II (Number and type of bond/s between two carbon atoms) |
|---|---|
| A. ethane | I. one \sigma-bond and two \pi-bonds |
| B. ethene | II. two \pi-bonds |
| C. carbon molecule, \mathrm{C}_{2} | III. one \sigma-bond |
| D. ethyne | IV. one \sigma-bond and one \pi-bond |
Choose the correct answer from the options given below:
(1) A-I, B-IV, C-II, D-III
(2) A-IV, B-III, C-II, D-I
(3) A-III, B-IV, C-II, D-I
(4) A-III, B-IV, C-I, D-II
Answer: Option (3)
Explanation:
In ethane, the two carbon atoms are joined by a single covalent bond,
which consists of one \sigma-bond only.
Therefore, ethane corresponds to III.
In ethene, the two carbon atoms are connected by a double bond,
which consists of one \sigma-bond and one \pi-bond.
Hence, ethene corresponds to IV.
The carbon molecule \mathrm{C}_{2} has two carbon atoms bonded by two \pi-bonds without any \sigma-bond.
Thus, \mathrm{C}_{2} corresponds to II.
In ethyne, the two carbon atoms are joined by a triple bond,
which consists of one \sigma-bond and two \pi-bonds.
Therefore, ethyne corresponds to I.
The correct matching is A-III, B-IV, C-II, D-I, which is option (3).