A-Level CIE Chemistry 1.2 Formulae, Equations & Calculations: 1 (a) (i) What is meant by the t

Question

1 (a) (i) What is meant by the term lattice energy?

Lattice energy refers to the amount of energy released when one mole of an ionic lattice is formed from its constituent gaseous ions. It is a measure of the strength of the forces between the ions in an ionic solid and is influenced by the charge and size of the ions involved.

(ii) Write an equation to represent the lattice energy of MgO.

$$ \text{Mg}^{2+} + \text{O}^{2-} \rightarrow \text{MgO(s)} $$

(b) The apparatus shown in the diagram can be used to measure the enthalpy change of formation of magnesium oxide, $ \Delta H_f^\circ(\text{MgO}) $.

List the measurements you would need to make using this apparatus in order to calculate $ \Delta H_f^\circ(\text{MgO}) $.

To accurately calculate the enthalpy change, the following measurements are needed:

- Volume/mass/weight of water used in the calorimeter
- Initial and final temperature/temperature change of the water
- Mass of magnesium ribbon used (to determine the amount of magnesium consumed)

(c) Use the following data, together with appropriate data from the Data Booklet, to calculate a value of $ \Delta H_f^\circ(\text{MgO}) $.

Lattice energy of MgO(s) = -3791 kJ mol⁻¹
Enthalpy change of atomisation of Mg = +148 kJ mol⁻¹
Electron affinity of the oxygen atom = -141 kJ mol⁻¹
Electron affinity of the oxygen anion, O⁻ = +798 kJ mol⁻¹

1 (a) (i) What is meant by the term lattice energy? Lattice energy refers to the amount of energy released when one mole of an ionic lattice is formed from its constituent gaseous ions - CIE - A-Level Chemistry - Question 1 - 2012 - Paper 1

Worked Solution & Example Answer:1 (a) (i) What is meant by the term lattice energy? Lattice energy refers to the amount of energy released when one mole of an ionic lattice is formed from its constituent gaseous ions - CIE - A-Level Chemistry - Question 1 - 2012 - Paper 1

What is meant by the term lattice energy?

Write an equation to represent the lattice energy of MgO.

List the measurements you would need to make using this apparatus in order to calculate \( \Delta H_f^\circ(\text{MgO}) \).

Use the following data, together with appropriate data from the Data Booklet, to calculate a value of \( \Delta H_f^\circ(\text{MgO}) \).

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