Chemistry 9701 · AS & A Level · Nitrogen and sulfur

Nitrogen and sulfur — practice question

Phosphorus, sulfur and chlorine are each able to react with oxygen and make oxides.
(a(i))[1]

When phosphorus reacts with excess oxygen, phosphorus(V) oxide is formed. Write an equation that represents phosphorus reacting with excess oxygen.

(a(ii))[2]

Describe how phosphorus(V) oxide reacts with water.

(a(iii))[1]

State the structure and bonding present in solid phosphorus(V) oxide.

(b(i))[2]

The two main oxides of sulfur are $\text{SO}_2$ and $\text{SO}_3$. When $\text{SO}_2$ dissolves in water, only a small fraction reacts with the water to produce a weak Brønsted-Lowry acid. Explain what is meant by the term weak Brønsted-Lowry acid.

(b(ii))[1]

Write the equation for the reaction between $\text{SO}_2$ and water.

(b(iii))[1]

$\text{SO}_2$ reacts with $\text{NO}_2$ in the atmosphere to form $\text{SO}_3$ and NO. NO is then oxidised in air to form $\text{NO}_2$. $\text{SO}_2 + \text{NO}_2 \rightarrow \text{SO}_3 + \text{NO}$ $2\text{NO} + \text{O}_2 \rightarrow 2\text{NO}_2$ State the role of $\text{NO}_2$ in this two-stage process.

(c(i))[1]

Emissions of $\text{SO}_2$ from coal-fired power stations can be lowered by mixing the coal with powdered limestone. Limestone is heated so that CaO is made in reaction 1. This then reacts with $\text{SO}_2$ and $\text{O}_2$ to form $\text{CaSO}_4$ in reaction 2. reaction 1: $\text{CaCO}_3(s) \rightarrow \text{CaO}(s) + \text{CO}_2(g)$ reaction 2: $\text{CaO}(s) + \text{SO}_2(g) + \tfrac{1}{2}\text{O}_2(g) \rightarrow \text{CaSO}_4(s)$ State the type of reaction occurring in reaction 1.

(c(ii))[2]

Using the data below, calculate the enthalpy change for reaction 2. $\Delta H_f / \text{kJ mol}^{-1}$: $\text{CaO}(s) = -635$, $\text{SO}_2(g) = -297$, $\text{CaSO}_4(s) = -1434$.

(d(i))[1]

Draw a ‘dot-and-cross’ diagram of $\text{Cl}_2\text{O}$. Include only the outer-shell electrons.

(d(ii))[1]

Write the oxidation state of chlorine in each species in the boxes provided. $\text{2NaClO}_2 + \text{Cl}_2 \rightarrow 2\text{ClO}_2 + 2\text{NaCl}$

(d(iii))[4]

$\text{Cl}_2\text{O}_6(g)$ is made by reacting $\text{ClO}_2(g)$ with $\text{O}_3(g)$. $2\text{ClO}_2(g) + 2\text{O}_3(g) \rightleftharpoons \text{Cl}_2\text{O}_6(g) + 2\text{O}_2(g) \qquad \Delta H = -216\,\text{kJ mol}^{-1}$ The reaction is carried out at $500\,\text{K}$ and $100\,\text{kPa}$. State and explain the effect on the yield of $\text{Cl}_2\text{O}_6(g)$ when the experiment is carried out: • at $1000\,\text{K}$ and $100\,\text{kPa}$ • at $500\,\text{K}$ and $500\,\text{kPa}$

(e(i))[2]

Suggest the type of bonding shown by the oxide of E. Explain your answer.

(e(ii))[2]

Suggest the type of bonding shown by the chloride of E. Explain your answer.

Worked solution & mark scheme

This 21-mark question has a full step-by-step worked solution and mark scheme. One marking point: $\mathrm{P_4 + 5O_2 \rightarrow P_4O_{10}}$

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