Chemistry 9701 · AS & A Level · Nitrogen compounds

Nitrogen compounds — practice question

Taken together, nitrogen and oxygen account for $99\%$ of air. Of the two gases, oxygen is much more reactive, and most substances that react with air combine with oxygen rather than nitrogen.
(a)[1]

State one explanation for why the nitrogen molecule, $\text{N}_2$, is so unreactive.

(b)[3]

Calculate the lattice energy of magnesium nitride with the data below, together with any relevant values from the Data Booklet.

(c(i))

Write an equation for how $\text{Li}_3\text{N}$ reacts with $\text{H}_2\text{O}$, and then identify compound $A$.\n\nReaction sequence:\n$\text{N}_2(g) + \text{Li} \rightarrow \text{Li}_3\text{N} \xrightarrow{+\,\text{H}_2\text{O}} \text{NH}_3 + A$

(c(ii))[3]

Using your knowledge of the Haber process, weigh up one advantage and one disadvantage of fixing nitrogen with lithium instead of using the Haber process.

(d(i))

Calculate the percentage by mass of nitrogen in $\text{Li}_3\text{N}$ and $\text{NH}_2\text{CONH}_2$, then compare the two values.

(d(ii))

Which class of organic compound does urea belong to?

(d(iii))

Write an equation showing how ammonia is produced when urea reacts with water.

(d(iv))[5]

Urea may be added straight to the soil either before crops are planted or during crop growth. What would be a major disadvantage of using lithium nitride in this way?

Worked solution & mark scheme

This 12-mark question has a full step-by-step worked solution and mark scheme. One marking point: “The $\ce{N#N}$ triple bond is (very) strong OR the $\ce{N2}$ molecule lacks polarity” …

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