Chemistry 9701 · AS & A Level · Electrochemistry

Electrochemistry — practice question

$\text{LiAlH}_4$ has $\text{AlH}_4^-$ ions, in which aluminium is in oxidation state $+3$. $\text{LiAlH}_4$ reacts with water, as follows. $\text{LiAlH}_4 + 4\text{H}_2\text{O} \rightarrow 4\text{H}_2 + \text{LiOH} + \text{Al(OH)}_3$ In this reaction, each of the four water molecules forms one hydroxide ion. This happens by losing one $\text{H}^+$ ion, which then reacts with the $\text{LiAlH}_4$. Which changes in oxidation number take place in this reaction?

  • AAl increases by $1$ and H decreases by $1$.
  • BH decreases by $2$ and also increases by $1$.
  • CH increases by $1$ and also decreases by $1$.
  • DO decreases by $1$ and H increases by $1$.

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