Chemistry 9701 · AS & A Level · States of matter

States of matter — practice question

Lead(II) chloride, $\text{PbCl}_2$, is used to make some coloured glass. $\text{PbCl}_2$ dissolves only slightly in water. The $[\text{Pb}^{2+}]$ in a saturated solution of $\text{PbCl}_2$ can be estimated by measuring the cell potential, $E_{\text{cell}}$, of the cell shown below.
(a)[4]

In the spaces provided, state what the four letters A-D in the diagram above stand for.

(b(i))

In a saturated solution of $\text{PbCl}_2$, $[\text{PbCl}_2$(aq)$] = 3.5 \times 10^{-2}\,\text{mol dm}^{-3}$. The $E^{\circ}$ for the $\text{Pb}^{2+}/\text{Pb}$ electrode is $-0.13\,\text{V}$. Predict the potential of the right-hand electrode in the diagram above. Show this by ticking the correct box in the table below and justify your answer.

(b(ii))

State an expression for the solubility product, $K_{sp}$, of $\text{PbCl}_2$.

(b(iii))[5]

Calculate the value of $K_{sp}$, including units.

(c(i))

The reactions of $\text{PbCl}_2$ and $\text{SnCl}_2$ with reducing agents are alike, but their reactions with oxidising agents are very different. Support this comparison by quoting and comparing the relevant $E^{\circ}$ values for the two metals and their ions. Explain what the relative $E^{\circ}$ values show about how easily these compounds are oxidised or reduced.

(c(ii))[5]

By writing a balanced molecular or ionic equation in each case, suggest a reagent that could be used for each of the following reactions: the reduction of $\text{PbCl}_2$; the oxidation of $\text{SnCl}_2$.

(d(i))

Write an equation to show the lattice energy of $\text{PbCl}_2$. Include state symbols.

(d(ii))

Use the data below, together with suitable data from the Data Booklet, to calculate a value for the lattice energy of $\text{PbCl}_2$: electron affinity of chlorine $= -349\,\text{kJ mol}^{-1}$; enthalpy change of atomisation of lead $= +195\,\text{kJ mol}^{-1}$; enthalpy change of formation of $\text{PbCl}_2(\text{s}) = -359\,\text{kJ mol}^{-1}$.

(d(iii))[6]

How would the lattice energy of $\text{PbCl}_2$ compare with that of $\text{PbBr}_2$? Explain your answer.

Worked solution & mark scheme

This 20-mark question has a full step-by-step worked solution and mark scheme. One marking point: A: potentiometer / V / voltmeter

  • Full mark scheme, point by point
  • Step-by-step worked solution
  • Write your answer & get it marked instantly by AI