Chemistry 9701 · AS & A Level · Chemical energetics

Chemical energetics — practice question

Silver, Ag, is one of the metals in the d-block of the Periodic Table.
(a)[1]

Silver can make compounds that contain either $\text{Ag}^+$ or $\text{Ag}^{2+}$ ions. Explain why silver is a transition element.

(b)

Table 1.1 contains the data needed for the Born-Haber cycle for silver(I) fluoride, $\text{AgF}$.

(b(i))[2]

Write equations for the standard enthalpy changes given below. Include state symbols. • standard enthalpy change of atomisation of silver • standard enthalpy change of formation of silver(I) fluoride

(b(ii))[2]

Define lattice energy.

(b(iii))[2]

Calculate the first electron affinity, $EA_1$, of fluorine, using the data in Table 1.1. Drawing a labelled energy cycle may help you with your answer.

(c(i))[1]

Use the information in Table 1.2 to calculate the enthalpy change of solution, $\Delta H_{sol}$, of $\text{AgF}$(s).

(c(ii))[1]

Use your answer to c(i) to suggest whether $\text{AgF}$ is soluble in water at $298\,\text{K}$. Explain your answer.

(d(i))[2]

Explain the trend in the first electron affinities of the halogens, $\text{Cl}$ to $\text{I}$.

(d(ii))[1]

Explain the trend in the lattice energies of the silver(I) halides, $\text{AgCl}$ to $\text{AgI}$.

(e(i))[2]

Calculate the standard cell potential, $E^\circ_{\text{cell}}$. Construct an equation for the overall cell reaction.

(e(ii))[3]

In another experiment, electrode 1 is prepared using a saturated KCl solution. Saturated KCl(aq) contains $36.0\,\text{g}$ of KCl per $100\,\text{cm}^3$ of solution at $298\,\text{K}$. The Nernst equation for electrode 1 is: $E = E^\circ + \frac{0.059}{z} \log \left( \frac{1}{[\text{Cl}^- (\text{aq})]} \right)$ Calculate the electrode potential, $E$, of electrode 1 under these conditions.

Worked solution & mark scheme

This 17-mark question has a full step-by-step worked solution and mark scheme. One marking point: $(\text{Ag}^{2+})$ forms stable ions with an incomplete $d$ subshell / incomplete $d$ orbitals

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