CAIE A-Level Chemistry AS 11.3 Some Reactions of the Halide Ions Questions

Practise halide reducing-strength trends, silver-ion tests and reactions with concentrated sulfuric acid.

Exam points

rank halide reducing strength and connect it to displacement or concentrated-acid redox
identify AgCl, AgBr and AgI from precipitate colour and their different behaviour with aqueous ammonia
write acid–base and redox equations for solid halides reacting with concentrated sulfuric acid

Covered syllabus points

11.3.1—Reactivity of halide ions as reducing agents 11.3.2—Reactions of halide ions

[Maximum number: 1]

The solids sodium chloride and sodium iodide both react with concentrated sulfuric acid at room temperature.

With NaCl , the products are $\mathrm{NaHSO}_{4}$ and HCl .
With NaI , the products are $\mathrm{NaHSO}_{4}, \mathrm{HI}, \mathrm{I}_{2}, \mathrm{SO}_{2}, \mathrm{H}_{2} \mathrm{O}, \mathrm{S}$ and $\mathrm{H}_{2} \mathrm{~S}$ .
What is the explanation for this difference in products?

Chloride ions will displace iodine from the solution.

Hydrogen chloride is more volatile than hydrogen iodide.

lodide ions are better reducing agents than chloride ions.

Sulfuric acid is able to act as a dehydrating agent with NaI .

[Maximum number: 2]

Hydrogen halides are compounds formed when halogens (Group 17 elements) react with hydrogen. The bond polarity of the hydrogen halides decreases from HF to HI.

Some relevant data are shown in the table.

Table for Question 2 — CAIE A-Level Chemistry AS

The equation for the preparation of hydrogen chloride using concentrated sulfuric acid is shown.

\mathrm{H}_{2} \mathrm{SO}_{4}+\mathrm{NaCl} \rightarrow \mathrm{NaHSO}_{4}+\mathrm{HCl}

Explain why the reaction of concentrated sulfuric acid and sodium iodide is not suitable for the preparation of hydrogen iodide.

$\mathrm{H}_{2} \mathrm{SO}_{4}$ is (too strong) an oxidising agent

$\mathrm{I}_{2}$ would be formed instead

[Maximum number: 1]

Chlorine is bubbled through a cylinder containing aqueous sodium iodide and an immiscible layer of hexane.

Figure for Question 3 — CAIE A-Level Chemistry AS

As the bubbles pass through the cylinder, what is observed in the lower and upper layers?

lower aqueous layer

upper hexane layer

colourless solution becomes brown

colourless liquid becomes coloured

colourless solution becomes brown

colourless liquid is unchanged

brown solution becomes colourless

colourless liquid becomes coloured

brown solution becomes colourless

colourless liquid is unchanged

All question bank results loaded

Covered syllabus points

Question 1

Question 2

Question 3