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

Chemistry of transition elements — practice question

Complexes are formed by transition elements.
(a(i))[1]

State the meaning of the term monodentate ligand.

(a(ii))[2]

Fill in the table by giving the formulae and charges of the complexes described: a molybdenum complex with one Mo atom surrounded by carbon monoxide, CO, molecules, and an iron(III) complex containing one $\text{Fe}^{3+}$ ion and several cyanide, $\text{CN}^-$, ions.

(a(iii))[1]

Draw a three-dimensional diagram showing the shape of this iron(III) complex. Mark one $180^{\circ}$ bond angle on your diagram.

(b(i))[1]

Excess aqueous ammonia is added to dilute copper(II) sulfate solution. A dark blue complex, $[\text{Cu}(\text{NH}_3)_4(\text{H}_2\text{O})_2]^{2+}$, forms. Write an ionic equation for this reaction.

(b(ii))[4]

Explain the cause of colour in copper(II) complexes.

(c(i))[2]

Write an equation for the formation of $Z$ from a solution of $[\text{Cu(NH}_3)_4(\text{H}_2\text{O})_2]^{2+}$. Include the formula and charge of $Z$.

(c(ii))[1]

Name the type of reaction when $Z$ is formed from $[\text{Cu(NH}_3)_4(\text{H}_2\text{O})_2]^{2+}$.

(c(iii))[1]

State the geometry of $Z$.

(c(iv))[1]

State the colour of a solution of $Z$.

(c(v))[1]

Explain why the colour of a solution of $[\text{Cu(NH}_3)_4(\text{H}_2\text{O})_2]^{2+}$ is different from the colour of a solution of $Z$. Refer to the energies of the orbitals involved in your answer.

Worked solution & mark scheme

This 15-mark question has a full step-by-step worked solution and mark scheme. One marking point: one lone pair is donated to a metal atom/ion, forming a dative bond

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