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Which of the following observations constitute evidence for the ionic nature of lithium hydride (LiH)? (A) Molten LiH (m.p. 691 deg C) conducts electricity. (B) Electrolysis of molten LiH liberates H2 gas at the anode. (C) LiH reacts with water to release H2 gas. (D) Electrolysis of molten LiH deposits Li metal at the cathode.

1. (A), (B) and (D)
2. (A), (C) and (D)
3. (B), (C) and (D)
4. (A), (B), (C) and (D)

Correct answer: (A), (B) and (D)

Solution

Molten LiH conducting electricity (A), H2 at the anode from H- oxidation (B), and Li deposition at the cathode from Li+ reduction (D) all directly prove ionic bonding. The reaction with water (C) is not exclusive to ionic hydrides.

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