Question 16

In an acidic medium, potassium ferricyanide ($K_3[Fe(CN)_6]$) reacts with potassium iodide ($KI$) in a redox reaction where $Fe^{3+}$ is reduced to $Fe^{2+}$ and $I^-$ is oxidized to $I_2$. The balanced chemical equation is:

$2K_3[Fe(CN)_6] + 2KI \rightarrow 2K_4[Fe(CN)_6] + I_2$

In this reaction, the complex $P$ is potassium ferrocyanide, $K_4[Fe(CN)_6]$. From the stoichiometry of the balanced equation, 2 moles of $KI$ are required to produce 2 moles of $P$. Therefore, the answer is 2.