Question

Given below are two statements:} Statement I:} The number of compounds among \(SO_2, SO_3, SF_4, SF_6\) and \(H_2S\) in which sulphur does not obey the octet rule is \(3\). Statement II:} Among \(H_2O, ClF_5, SF_4, [NH_3BF_3], [BrF_5Cl], ClF_3, XeF_4\) and \([XeF_4, ClF_3(H_2O)]\), the number of sets in which the molecules have one lone pair of electrons on the central atom is \(1\). Choose the correct answer.

• A. Both Statement I and Statement II are true
• B. Both Statement I and Statement II are false
• C. Statement I is true but Statement II is false
• D. Statement I is false but Statement II is true

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
We need to evaluate statements regarding the octet rule for sulphur compounds and the number of lone pairs on central atoms for various sets of molecules.
Step 2: Key Formula or Approach:
- Octet rule: Atoms share electrons to have 8 in the valence shell. Molecules with more than 8 (hypervalent) or fewer than 8 (hypovalent) do not obey it.
- Lone pair calculation: \(\text{LP} = \frac{1}{2}[\text{Valence electrons} - \text{Atoms bonded}]\) for neutral atoms.
Step 3: Detailed Explanation:
1. Statement I:
- \(\text{H}_2\text{S}\): S has 8 electrons (2 BP + 2 LP). Obeys.
- \(\text{SO}_2\): S has 10 electrons in some resonance structures (expanded octet). Usually considered hypervalent.
- \(\text{SO}_3, \text{SF}_4, \text{SF}_6\): All have expanded octets (12, 10, 12 valence electrons respectively).
- Thus, \(\text{SO}_3, \text{SF}_4, \text{SF}_6\) (3 compounds) clearly do not obey. Statement I is True.
2. Statement II:
- Set 1: \(\text{H}_2\text{O}\) (2 LP), \(\text{ClF}_3\) (2 LP), \(\text{SF}_4\) (1 LP).
- Set 2: \(\text{NH}_3\) (1 LP), \(\text{BrF}_5\) (1 LP), \(\text{SF}_4\) (1 LP). All have exactly 1 lone pair.
- Set 3: \(\text{BrF}_5\) (1 LP), \(\text{ClF}_3\) (2 LP), \(\text{XeF}_4\) (2 LP).
- Set 4: \(\text{XeF}_4\) (2 LP), \(\text{ClF}_3\) (2 LP), \(\text{H}_2\text{O}\) (2 LP).
- Only Set 2 qualifies. So the number of sets is indeed 1. Statement II is True.
Step 4: Final Answer:
Both statements are true.