CAIE A-Level Chemistry 23.1.4 Born–Haber Cycle Calculations

Practise using Hess’s law in Born–Haber cycles to calculate lattice energy, atomisation or electron affinity.

Exam points

select only the enthalpy terms lying on a complete alternative route between the same states
multiply atomisation, ionisation or affinity terms by the ionic formula coefficients
preserve each data sign and solve the cycle algebraically for the single unknown enthalpy

[Maximum number: 3]

Calcium metal reacts with chlorine gas to form calcium chloride, $\mathrm{CaCl}_{2}$ .

Use your answer to (ii) and the following data, together with relevant data from the Data Booklet, to calculate a value for $\Delta H_{\text {latt }}^{\ominus}$ for calcium chloride.

Table for Question 23.1.4—Calculations: Born–Haber cycles question 1 — CAIE A-Level Chemistry A2

\Delta H_{\text {latt }}^{\ominus}=\ldots \ldots \ldots \ldots \ldots . . . . . . . . . . . . . . . . . . . . k J ~ m o l-1 ~

$\Delta \mathrm{H}_{\text {latt }}{ }^{\theta}=-796-242-178-590-1150+(2 \times 349)=-2258 \mathrm{~kJ} \mathrm{~mol}^{-1}$

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23.1.4—Calculations: Born–Haber cycles question 1