Chemistry 9701 · AS & A Level · Group 2

Group 2 — practice question

(a)[1]

Group 2 nitrates break down when heated. Write an equation for the decomposition of strontium nitrate.

(b)[3]

Describe and explain how the thermal stability of Group 2 nitrates varies as the atomic number increases down the group.

(c(i))[1]

The pattern in the thermal stability of Group 2 amides is similar to that of Group 2 nitrates. Suggest whether calcium amide, $\text{Ca(NH}_2)_2$, will decompose more or less readily than barium amide, $\text{Ba(NH}_2)_2$. Explain your answer.

(c(ii))[1]

$\text{Ba(NH}_2)_2$ decomposes on heating to produce barium nitride, $\text{Ba}_3\text{N}_2$, and ammonia as the only products. Write an equation for this reaction.

(d)[3]

$\text{Ba(NH}_2)_2$ contains the $\text{NH}_2^-$ ion. Predict the bond angle of $\text{NH}_2^-$. Explain your answer using the qualitative model of electron-pair repulsion. bond angle; explanation.

Worked solution & mark scheme

This 9-mark question has a full step-by-step worked solution and mark scheme. One marking point: Equation: $Sr(NO_3)_2 \rightarrow SrO + 2NO_2 + \tfrac{1}{2}O_2$

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