Question

A yellow compound X is produced after the reaction of \( K_2[Ni(CN)_4] \) with excess of \( K/\text{liq. NH}_3 \) at -33°C. The oxidation state of Ni in the compound X is ..........

Hint:

In reactions where excess ammonia is used, often a reduction of the metal ion occurs, resulting in a change in oxidation state. For nickel, this often leads to a Ni(0) complex.

Answer 1

The given compound is \( K_2[Ni(CN)_4] \), where the oxidation state of Ni is +2. On reacting with excess \( K/\text{liq. NH}_3 \), a yellow compound is formed. This typically suggests a reduction of Ni(II) to Ni(0) since yellow complexes are often associated with nickel in the zero oxidation state. Thus, the oxidation state of Ni in compound X is 0.
Final Answer: \[ \boxed{0} \]