Chemistry 9701 · AS & A Level · Nitrogen and sulfur

Nitrogen and sulfur — practice question

Nitrogen, $\text{N}_2$, is the most plentiful gas in the Earth’s atmosphere and is highly unreactive.
(a)[1]

State why $\text{N}_2$ reacts very little.

(b(i))[1]

Write an equation showing the reaction of magnesium with $\text{N}_2$ to produce magnesium nitride.

(b(ii))[1]

Solid lithium nitride, $\text{Li}_3\text{N}$(s), reacts with water as shown below. $\text{Li}_3\text{N}$(s) $+\ 3\text{H}_2\text{O}$(l) $\rightarrow\ 3\text{LiOH}$(aq) $+\ \text{NH}_3$(aq) State one observation you would make during this reaction.

(c(i))[1]

State one industrial use of ammonia.

(c(ii))[2]

One way to produce $\text{NH}_3$ is by heating ammonium chloride, $\text{NH}_4\text{Cl}$, with $\text{CaO}$. $2\text{NH}_4\text{Cl} + \text{CaO} \rightarrow 2\text{NH}_3 + \text{CaCl}_2 + \text{H}_2\text{O}$ Explain why heating $\text{NH}_4\text{Cl}$ with $\text{CaO}$ gives ammonia.

(d(i))[1]

Complete the table by filling in the oxidation numbers of nitrogen in $\text{NO}$ and $\text{NO}_2$.

(d(ii))[2]

$\text{NO}_2$ can be made by different chemical reactions. Write equations for the formation of $\text{NO}_2$ by: - the reaction of $\text{N}_2$ with $\text{O}_2$ - the thermal decomposition of magnesium nitrate.

(d(iii))[2]

Molecules of $\text{N}_2\text{O}$ may be made by the reaction between $\text{N}_2$ and $\text{O}_2$. The bond linking the N and O atoms $(\text{N}\rightarrow\text{O})$ is a co-ordinate (dative covalent) bond. $2\text{N}_2$(g) $+\ \text{O}_2$(g) $\rightarrow 2\text{N}\equiv\text{N}\rightarrow\text{O}$(g) The enthalpy change of reaction for this reaction is $+82\ \text{kJ mol}^{-1}$. Calculate the bond enthalpy, in $\text{kJ mol}^{-1}$, of the $\text{N}\rightarrow\text{O}$ bond. Use relevant data from the Data Booklet to answer this question.

(e)[2]

Nitrosyl chloride, $\text{NOCl}$, is a reactive gas that is sometimes produced when $\text{NO}$ reacts with $\text{Cl}_2$. $\text{NOCl}$ is a strong electrophile and readily takes part in an addition reaction with alkenes. Complete the diagram to show the mechanism of the electrophilic addition reaction of $\text{NOCl}$ with ethene. Include all necessary charges, lone pairs and curly arrows, and the structure of the organic intermediate.

Worked solution & mark scheme

This 13-mark question has a full step-by-step worked solution and mark scheme. One marking point: Very strong triple bond / strong $\mathrm{N\equiv N}$ OR high activation energy $E_a$ OR non-polar

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