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

Chemistry of transition elements — practice question

(a)[1]

Some atomic orbitals are shown as sketches of their shapes. Identify whether each orbital is $s$, $p$ or $d$.

(b)[1]

Cadmium forms the two ions $\text{Cd}^{2+}$ and $\text{Cd}^+$. Their electronic configurations are shown below: • $[\text{Kr}]\,4d^{10}5s^1$ • $[\text{Kr}]\,4d^{10}$ 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 monodentate means in this context.

(c(ii))[2]

In aqueous methylamine, $[\text{Cd}(\text{H}_2\text{O})_6]^{2+}$ reacts to give a mixture of two octahedral isomers. equilibrium 1: $[\text{Cd}(\text{H}_2\text{O})_6]^{2+} + 4\text{CH}_3\text{NH}_2 \rightleftharpoons [\text{Cd}(\text{CH}_3\text{NH}_2)_4(\text{H}_2\text{O})_2]^{2+} + 4\text{H}_2\text{O}$, $\Delta H^\circ = -57\,\text{kJ mol}^{-1}$ Complete the three-dimensional 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 the term stability constant means.

(d(ii))[2]

Complete the table by putting one tick ($\checkmark$) in each row to indicate how a higher temperature would change the stability constant, $K_{\text{stab}}$, 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.

(e)[1]

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

(f(i))[2]

Write an equation for the reaction between ethanoyl chloride and methylamine.

(f(ii))[1]

Methylamine also reacts with propanone to make compound P as shown. Deduce the reaction type shown.

Worked solution & mark scheme

This 12-mark question has a full step-by-step worked solution and mark scheme. One marking point: The correct shapes for the $p$, $s$ and $d$ orbitals are shown.

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