The Reactions of Chlorine (Cambridge (CIE) A Level Chemistry): Exam Questions

Chlorine reacts with cold aqueous sodium hydroxide.

i) Construct an equation for this reaction.

[1]

ii) State the name of the product containing both oxygen and chlorine.

[1]

iii) Explain, in terms of changes in oxidation number, why this reaction is an example of a disproportionation reaction.

[2]

Chlorine is added to drinking water to ensure that it is safe to drink.

i) Construct an equation for the reaction of chlorine with cold water.

[1]

ii) Identify the two active species produced in this reaction that are responsible for killing bacteria.

[1]

One of the products formed in part (b)(i) is classified as a weak acid.

State which product is the weak acid and construct an equation to show its behaviour as a weak acid.

weak acid:

equation:

When chlorine reacts with hot aqueous sodium hydroxide, a different product is formed.

Give the formula of the different product and deduce the oxidation state of the chlorine atom in this compound.

formula:

oxidation state of chlorine:

Chlorine reacts with cold aqueous sodium hydroxide.

i) Construct an equation for this reaction.

[1]

ii) Name the product that contains both chlorine and oxygen, and state one commercial use of the solution formed.

[1]

iii) Explain, in terms of changes in oxidation number, why this reaction is an example of a disproportionation reaction.

[2]

When chlorine reacts with water, the following equilibrium is established.

Cl₂ (aq) + H₂O (l) ⇌ H⁺ (aq) + Cl^– (aq) + HClO (aq)

i) Deduce the oxidation state of Cl in HClO.

[1]

ii) Deduce what happens to the position of this equilibrium as the HClO reacts with bacteria in the water supply. Explain your answer.

[2]

Suggest one disadvantage of treating drinking water with chlorine.

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

Chlorine is added to drinking water to kill harmful bacteria and make it safe to drink. During this process, chlorine undergoes a disproportionation reaction.

i) Construct an equation for this reaction.

[1]

ii) Deduce the oxidation number of chlorine in each of the chlorine-containing products formed.

[1]

The reaction of chlorine with water can be described as a disproportionation reaction. Chlorine also undergoes a disproportionation reaction when it reacts with hot aqueous sodium hydroxide.

i) Construct an equation for the reaction of chlorine with hot aqueous sodium hydroxide.

[1]

ii) Explain, in terms of changes in oxidation number, why this is also an example of a disproportionation reaction.

[2]

The halogens can react with iron wool to produce various iron compounds including iron(III) chloride, iron(III) bromide and iron(II) iodide.

The Fe²⁺ ion can also react with chlorine, Cl₂, and bromine, Br₂.

i) Construct an ionic half-equation for the reduction of bromine.

[1]

ii) Construct an ionic half-equation for the oxidation of Fe²⁺ to Fe³⁺.

[1]

iii) Hence, construct an overall equation for the reaction of Br₂ with Fe²⁺.

[1]

iv) Explain why iodine does not oxidise Fe²⁺ ions.

[1]

The bromate(V) ion, BrO₃^–, is formed when bromide ions react with hypochlorous acid, HClO, in aqueous alkali, as shown in the equation.

Br^– + 3HClO + 3OH^– → BrO₃^– + 3Cl^– + 3H₂O

Deduce the oxidation number of chlorine in HClO and in Cl^–.

oxidation number of Cl in HClO:

oxidation number of Cl in Cl^–:

Identify the oxidising agent in the reaction in part (b). Explain your answer.