Chemistry 9701 · AS & A Level · Group 17

Group 17 — practice question

The Group 17 elements, called the halogens, exhibit patterns in both chemical and physical properties. Their elements and compounds are employed in a wide range of ways.
(a(i))[1]

At room temperature fluorine and chlorine are gases, bromine is a liquid and iodine is a solid. State how volatility changes down Group 17.

(a(ii))[2]

Explain why this pattern occurs.

(b)[1]

Iodine, $\text{I}_2$, is displaced from $\text{NaI(aq)}$ by chlorine, $\text{Cl}_2$. Write an equation for this reaction.

(c(i))[3]

Silver nitrate solution, $\text{AgNO}_3(aq)$, is added to separate solutions of $\text{NaI}$ and $\text{NaCl}$. Precipitates form. Excess aqueous ammonia is then added to both precipitates. Complete the table with the colour and name of the precipitate produced in each reaction, and with what happens when excess aqueous ammonia is added to each precipitate.

(c(ii))[1]

Write an ionic equation, including state symbols, to show the reaction taking place when $\text{AgNO}_3(aq)$ is added to $\text{NaI(aq)}$.

(d)[3]

Solid $\text{NaI}$ reacts with concentrated sulfuric acid to give purple fumes of $\text{I}_2\text{(g)}$ and hydrogen sulfide gas, $\text{H}_2\text{S\,(g)}$. By contrast, when solid $\text{NaCl}$ reacts with concentrated sulfuric acid, the only gas formed is $\text{HCl\,(g)}$. Explain why concentrated sulfuric acid reacts differently with $\text{NaI}$ and with $\text{NaCl}$. Your answer should mention the role of the sulfuric acid in each case.

(e(i))[1]

Explain what is meant by oxidising agent in terms of electron transfer.

(e(ii))[1]

Suggest an equation for the reaction between chlorine and water.

(e(iii))[2]

Write an equation for the reaction between chlorine and hot aqueous sodium hydroxide. Use oxidation numbers to explain why this counts as a redox reaction.

Worked solution & mark scheme

This 15-mark question has a full step-by-step worked solution and mark scheme. One marking point: Volatility falls

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