Chemistry 9701 · AS & A Level · Chemistry of transition elements

Chemistry of transition elements — practice question

(a)[1]

The diagrams show the shapes of several atomic orbitals. Name the orbital type, $s$, $p$, or $d$.

(b)[1]

Cadmium gives the two ions, $\text{Cd}^{2+}$ and $\text{Cd}^+$. The electronic configuration of cadmium in these ions is shown as $[\text{Kr}]\,4d^{10}5s^1$ and $[\text{Kr}]\,4d^{10}$. Use this information to explain why cadmium is not a transition element.

(c(i))[1]

Methylamine, $\text{CH}_3\text{NH}_2$, is a monodentate ligand. State what is meant by monodentate in this context.

(c(ii))[2]

When aqueous methylamine is present, $[\text{Cd}(\text{H}_2\text{O})_6]^{2+}$ reacts to produce a mixture of two octahedral isomers. Equilibrium 1: $[\text{Cd}(\text{H}_2\text{O})_6]^{2+} + 4\text{CH}_3\text{NH}_2 \rightleftharpoons [\text{Cd}(\text{CH}_3\text{NH}_2)_4(\text{H}_2\text{O})_2]^{2+} + 4\text{H}_2\text{O}$, $\Delta H^\circ = -57\,\text{kJ mol}^{-1}$ Finish the 3D diagrams to show the isomers of $[\text{Cd}(\text{CH}_3\text{NH}_2)_4(\text{H}_2\text{O})_2]^{2+}$. Use $L$ to represent $\text{CH}_3\text{NH}_2$ in your diagrams.

(d(i))[1]

State what is meant by the term stability constant.

(d(ii))[2]

Complete the table by putting one tick (✓) in each row to show how increasing temperature is expected to change $K_{\text{stab}}$ and the equilibrium concentration of the cadmium complex, $[[\text{Cd}(\text{CH}_3\text{NH}_2)_4(\text{H}_2\text{O})_2]^{2+}]$, for equilibrium 1. Explain your answer.

(c(iii))[1]

A solution containing equal amounts of $\text{CH}_3\text{NH}_2$ and EDTA is added to $[\text{Cd(H}_2\text{O)}_6]^{2+}$. Predict which complex is formed in the larger amount. Explain your answer.

(e)[1]

Methylamine is a Brønsted-Lowry base. Write an equation to show how methylamine dissolves in water to produce an alkaline solution.

(f(i))[2]

Write an equation for the reaction of ethanoyl chloride with methylamine.

(f(ii))[1]

Methylamine also reacts with propanone to form compound $P$ as shown. Deduce the reaction type shown here.

Worked solution & mark scheme

This 13-mark question has a full step-by-step worked solution and mark scheme. One marking point: Accurate shapes for $p$, $s$ and $d$ orbitals

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