Chemistry 9701 · AS & A Level · States of matter

States of matter — practice question

(a(i))[1]

State what is meant by a transition element.

(a(ii))[1]

Explain why transition elements are able to form complex ions.

(b(i))[1]

The $3d$ orbitals in an isolated $\text{Ag}^+$ ion 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 useful for telling aldehydes apart from ketones. Tollens’ reagent contains $[\text{Ag(NH}_3)_2]\text{OH}$, which is prepared in two stages. Step 1: Aqueous NaOH is added dropwise to aqueous $\text{AgNO}_3$ to produce $\text{Ag}_2\text{O}$ as a brown precipitate. Step 2: Aqueous $\text{NH}_3$ is then added dropwise to $\text{Ag}_2\text{O}$ to give a colourless solution of $[\text{Ag(NH}_3)_2]\text{OH}$. Write equations for each stage in the preparation of $[\text{Ag(NH}_3)_2]\text{OH}$.

(d)[2]

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

(e)[2]

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

(f)[2]

Coordination polymers form when a bidentate ligand bridges between separate metal ions. Under certain conditions $\text{Ru}^{3+}$(aq) and the bidentate ligand $dps$ can make a coordination polymer with $\left[\text{Ru}(dps)\text{Cl}_4\right]_n^-$ chains. The bidentate ligand $dps$ uses each nitrogen atom to bond to a different $\text{Ru}^{3+}$. Complete Fig. 2.3 by drawing the structure of the coordination polymer $\left[\text{Ru}(dps)\text{Cl}_4\right]_n^-$. Show two 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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