States of Matter and Electrolytic Conductivity

Steps:

• Identify states at room temperature and pressure: NaI (X) is ionic solid (mp 661°C); CH3I (Y) is covalent liquid (bp 42°C).
• Determine gap 1: Only X (NaI) is solid; Y is liquid.
• Assess conductivity in aqueous solution: Ionic solids like NaI dissolve into Na⁺ and I⁻ ions, conducting electricity; covalent CH3I does not ionize.
• Match to option: Gap 1 "only X is [solid]"; gap 2 "only X conducts [electricity]".

Why D is correct:

• D fits because NaI is the only solid (ionic lattice) that dissociates into ions in water, per electrolytic conduction definition for strong electrolytes.

Why the others are wrong:

• A: Both are not solids; CH3I is liquid, and it doesn't conduct.
• B: Y (CH3I) is not solid and doesn't conduct as a non-electrolyte.
• C: Gap 2 wrongly states only Y conducts; Y is non-ionic and non-conducting.

Final answer: D