Question 1

Paper 2Medium6 marks

Carbon monoxide can be formed by the incomplete combustion of graphite and can be oxidized further to carbon dioxide. At 298 K, the standard enthalpy changes for the following reactions are:

C(graphite, s) + O₂(g) → CO₂(g)  ΔH° = −393.5 kJ mol⁻¹

CO(g) + ½O₂(g) → CO₂(g)  ΔH° = −283.0 kJ mol⁻¹

(a)

Write a balanced equation, including state symbols, for the formation of exactly 1 mol of CO(g) from its elements in their standard states.

[1]
(b)

Construct an energy cycle using the information above and your equation in (a), then calculate the standard enthalpy change for the formation of CO(g). Give your answer in kJ mol⁻¹.

[3]
(c)

Using the sign of your answer in (b), explain what it indicates about the direction of energy transfer and the relative enthalpy of the products and reactants.

[2]

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