Question

Hydrogen gas will not reduce:

• A. heated cupric oxide
• B. heated ferric oxide
• C. heated stannic oxide
• D. heated aluminium oxide

Answer 1

The correct option is D heated aluminium oxide

According to electrochemical series,
Al is more electropositive than H so it can not be reduced by hydrogen gas.
Fe and Sn are also more electropositive than H but they are reduced from $F{e}^{3+}$ to $F{e}^{2+};S{n}^{4+}$ to $S{n}^{2+}$. a lower oxidation state.