Question

Oxidation number of H in NaH, CaH$_2$, and LiH, respectively is:

• A. +1, +1, -1
• B. -1, +1, +1
• C. +1, +1, +1
• D. -1, -1, -1

Hint:

In metal hydrides (e.g., NaH, CaH$_2$, LiH), hydrogen acts as a hydride ion (\( H^- \)) with an oxidation number of \(-1\). This is different from most other compounds, where hydrogen typically has an oxidation number of \(+1\).

Answer 1

The Correct Option is D

1. Oxidation Number in NaH (Sodium Hydride)
Sodium (\(Na\)) is an alkali metal with a fixed oxidation number of \(+1\).
Since NaH is a neutral compound, hydrogen must have an oxidation number of \(-1\) to balance the charge. 2. Oxidation Number in CaH$_2$ (Calcium Hydride)
Calcium (\(Ca\)) is an alkaline earth metal with an oxidation number of \(+2\).
Since CaH$_2$ is neutral, hydrogen must have an oxidation number of \(-1\) to balance the charge. 3. Oxidation Number in LiH (Lithium Hydride)
Lithium (\(Li\)) is an alkali metal with an oxidation number of \(+1\).
Since LiH is neutral, hydrogen must have an oxidation number of \(-1\) to balance the charge. Final Answer: Option (d) \(-1, -1, -1\).