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

Chemistry of transition elements — practice question

(a(i))[1]

Define transition element clearly.

(a(ii))[1]

Explain why transition elements are able to form complex ions.

(b(i))[1]

In an isolated $\text{Ag}^+$ ion, the $3d$ orbitals are degenerate. Define degenerate $d$ orbitals.

(b(ii))[1]

Sketch the shape of a $3d_{xy}$ orbital in Fig. 2.1.

(c)[2]

Tollens’ reagent is used to tell aldehydes apart from ketones. Tollens’ reagent contains $[\text{Ag(NH}_3)_2]\text{OH}$, and this can be made in two steps. Step 1: Aqueous $\text{NaOH}$ is added dropwise to aqueous $\text{AgNO}_3$ so that $\text{Ag}_2\text{O}$ forms as a brown precipitate. Step 2: Aqueous $\text{NH}_3$ is added dropwise to $\text{Ag}_2\text{O}$ to give a colourless solution containing $[\text{Ag(NH}_3)_2]\text{OH}$. Construct equations for each stage in making $[\text{Ag(NH}_3)_2]\text{OH}$.

(d)[2]

State the shape of the complex ion $[\text{Ag(NH}_3)_2]^+$. State the bond angle for H-N-Ag and for N-Ag-N.

(e)[2]

An electrochemical cell has $\text{Ag}_2\text{O}$ as the positive electrode and Zn as the negative electrode, both in an alkaline electrolyte. The overall cell reaction is: $\text{Ag}_2\text{O} + \text{Zn} + \text{H}_2\text{O} \rightarrow 2\text{Ag} + \text{Zn(OH)}_2$ Complete the half-equation for the process at each electrode: At the positive electrode: $\text{Ag}_2\text{O} + \ldots$ At the negative electrode: $\text{Zn} + \ldots$

(f)[2]

Complete Fig. 2.3 by drawing the structure of the coordination polymer $[\{\text{Ru(dps)Cl}_4\}_n^-]$. Include three repeat units.

Worked solution & mark scheme

This 12-mark question has a full step-by-step worked solution and mark scheme. One marking point: An element that forms one or more stable ions with incomplete $d$ orbitals

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