Question 16

Nickel is an important transition metal.

Three of the stages in the extraction and purification of nickel using the Mond process are:

Stage 1: nickel(II) oxide is reduced by heating with $H2\text{H}_2$ to produce impure nickel:

\text{NiO(s)} + \text{H}_2\text{(g)} \rightarrow \text{Ni(s)} + \text{H}_2\text{O(g)}

Stage 2: the impure nickel is reacted with carbon monoxide to produce gaseous nickel tetracarbonyl:

\text{Ni(s)} + 4\text{CO(g)} \rightleftharpoons \text{Ni(CO)}_4\text{(g)}

Stage 3: $Ni(CO)4\text{Ni(CO)}_4$ is decomposed by heating to produce pure nickel:

\text{Ni(CO)}_4\text{(g)} \rightarrow \text{Ni(s)} + 4\text{CO(g)}

(i) State why the reaction in Stage 1 is described as reduction.

(ii) Suggest why a low temperature produces a high yield of $Ni(CO)4\text{Ni(CO)}_4$ in Stage 2.

Nickel has a melting point of $1455∘C1455^\circ\text{C}$ and is an excellent conductor of electricity.

(i) Describe the arrangement and charges of the particles in metallic nickel.

(ii) Explain, in terms of its structure, why nickel is malleable and is a good conductor of electricity.