Chemistry 0620 · IGCSE · Reversible reactions and equilibrium

Reversible reactions and equilibrium — practice question

Chlorine reacts with carbon monoxide to form phosgene gas, COCl$_2$(g). A catalyst is employed. Cl$_2$(g) + CO(g) ⇌ COCl$_2$(g) The reaction is exothermic.
(a)[3]

Explain why the reaction is exothermic by referring to the energy changes during bond breaking and bond making.

(b(i))[3]

Complete the energy level diagram for this reaction. On your diagram include: the product of the reaction; an arrow showing the energy change, labelled $\Delta H$; an arrow showing the activation energy, labelled A.

(b(ii))[1]

State why a catalyst is added.

(c(i))[2]

Describe and explain what happens, if anything, to the position of equilibrium when the pressure is increased.

(c(ii))[2]

Describe and explain what happens, if anything, to the position of equilibrium when the temperature is increased.

(d)[3]

Use the information provided to calculate the bond energy of the C and O bond in carbon monoxide, CO.

(e)[3]

Complete the dot-and-cross diagram to show the electron arrangement in a molecule of COCl$_2$. Show outer electrons only.

Worked solution & mark scheme

This 17-mark question has a full step-by-step worked solution and mark scheme. One marking point: Energy released when bonds form is greater than energy needed for bond breaking

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