Chemistry 0620 · IGCSE · Reversible reactions and equilibrium

Reversible reactions and equilibrium — practice question

Carbonyl chloride, COCl₂, is made by reacting carbon monoxide with chlorine. $\text{CO(g)} + \text{Cl}_2(\text{g}) \rightleftharpoons \text{COCl}_2(\text{g}) \quad \Delta H = -105\,\text{kJ/mol}$ This reaction is carried out in a closed system until equilibrium is established. The conditions used are 200 ^{\circ}C and 200 kPa.
(a)[1]

Explain the meaning of a closed system.

(b)[1]

State the quantity represented by the symbol ΔH.

(c)[1]

State how the sign of ΔH shows that the forward reaction is exothermic.

(d)[1]

Deduce the value of ΔH for the reverse reaction. Make sure your answer includes a sign.

(e)[4]

Complete Table 4.1 to show the effect, if any, on the equilibrium concentration of COCl₂(g) when the conditions below are changed. Use only the words increases, decreases or no change.

(f)[3]

Use the bond energies in Table 4.2 together with the value of ΔH for the reaction to Calculate the bond energy, in kJ/mol, of the C=O bond. Calculate the energy required to break the bonds in the reactants. Calculate the energy released when the bonds in carbonyl chloride are formed. Calculate the bond energy of the C=O bond.

(g)[3]

Finish the dot-and-cross diagram in Fig. 4.2 for a molecule of carbonyl chloride. Show only the outer shell electrons.

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