Chemistry 9701 · AS & A Level · Nitrogen and sulfur

Nitrogen and sulfur — practice question

Nitrogen dioxide, $\text{NO}_2$, may enter the atmosphere by several different routes.
(a(i))[1]

State one natural source and one man-made source of atmospheric $\text{NO}_2$.\n\nnatural ________\n\nman-made ________

(a(ii))[1]

Write an equation to show how $\text{NO}_2$ brings about the formation of nitric acid in acid rain.

(a(iii))[3]

Use equations to show the catalytic function of $\text{NO}_2$ in producing sulfuric acid in acid rain.

(b(i))[1]

Nitrogen dioxide is in equilibrium with dinitrogen tetroxide, $\text{N}_2\text{O}_4$.\n\n$\text{2NO}_2(\text{g}) \rightleftharpoons \text{N}_2\text{O}_4(\text{g})$\n\n$2.00\,\text{mol}$ of dinitrogen tetroxide was placed in a sealed container at $350\,\text{K}$. Once equilibrium had been reached the total pressure was $140\,\text{kPa}$ and the gas mixture contained $1.84\,\text{mol}$ of dinitrogen tetroxide.\n\nGive the expression for the equilibrium constant, $K_p$, for this equilibrium.

(b(ii))[1]

Calculate how many moles of $\text{NO}_2$ are present at equilibrium.

(b(iii))[2]

Calculate the total number of moles of gas at equilibrium and then determine the mole fraction of each gas at equilibrium.

(b(iv))[2]

Calculate the partial pressures for each gas present at equilibrium.

(b(v))[2]

Calculate the value of $K_p$ at $350\,\text{K}$. Give your answer to three significant figures and include the units.

(iv)[2]

Calculate the partial pressures of all gases present at equilibrium.

(v)[2]

Calculate the value of the equilibrium constant, $K_p$, at $350\,\text{K}$. Provide the answer to three significant figures and include the units.

Worked solution & mark scheme

This 17-mark question has a full step-by-step worked solution and mark scheme. One marking point: Reaction of atmospheric $\text{N}_2$ and $\text{O}_2$ in lightning or through biological processes or soil bacteria AND emissions from car engines or power stations or metal refining or furnaces

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