(a)

Chlorine undergoes disproportionation during many chemical reactions.

[ 3 ]

(i)

Write an equation for the reaction of chlorine with cold aqueous sodium hydroxide, NaOH .

Explain why it is a disproportionation reaction.
equation
explanation

[ 2 ]

(ii)

One of the products of the reaction of chlorine with hot aqueous sodium hydroxide differs from those in (c)(i).

Identify the compound that is formed in this reaction that is different from that formed in the reaction in (c)(i).

[ 1 ]

(b)

State and explain the use of chlorine in water purification.

[ 2 ]

(a)

Some reactions involving chlorine and its compounds are shown in the reaction scheme below.

[ 8 ]

(i)

Give the formulae of W, X, Y and Z.

W
X
Y
Z

[ 4 ]

(ii)

Write an equation for the reaction of chlorine with hot NaOH(aq).

[ 2 ]

(iii)

State the oxidation numbers of chlorine at the start and at the end of the reaction in (ii).

[ 2 ]

[Maximum number: 1]

The elements in Group 17 are known as the halogens.

(a)

Bleach is made by reacting $\mathrm{Cl}_{2}$ with cold NaOH(aq).

Write an equation for the reaction of $\mathrm{Cl}_{2}$ with cold NaOH .

[ 1 ]

[Maximum number: 1]

HOCl(aq) is the molecule that kills bacteria when chlorine is added to water.
The following reaction produces this molecule.

\mathrm{Cl}_{2}(\mathrm{~g})+\mathrm{H}_{2} \mathrm{O}(\mathrm{l}) \rightleftharpoons \mathrm{HOCl}(\mathrm{aq})+\mathrm{H}^{+}(\mathrm{aq})+\mathrm{Cl}^{-}(\mathrm{aq})

Which statement about this reaction is correct?

Chlorine is both oxidised and reduced.

Chlorine is oxidised but not reduced.

Hydrogen is both oxidised and reduced.

Hydrogen is oxidised but not reduced.

[Maximum number: 2]

Chlorine, $\mathrm{Cl}_{2}$ , is a reactive yellow-green gas. It is a strong oxidising agent.

(a)

State how $\mathrm{Cl}_{2}$ is used in water purification.

[ 1 ]

(b)

$\mathrm{Cl}_{2}$ reacts with aqueous sodium hydroxide in a disproportionation reaction.

[ 1 ]

(i)

Write an equation for the reaction of $\mathrm{Cl}_{2}$ with cold aqueous sodium hydroxide.

[ 1 ]

[Maximum number: 3]

Chlorine is a reactive element. It forms many compounds.

(a)

(i)

Write an equation for the reaction of chlorine with water.

[ 1 ]

(ii)

Write an equation for the reaction of chlorine with hot NaOH(aq).

[ 1 ]

(b)

Bleach is used as a cleaning product to kill bacteria. It is made by adding compounds like sodium chlorate(I), NaClO, to water.

[ 1 ]

(i)

Identify the formula of the ion present in bleach that kills bacteria.

[ 1 ]

[Maximum number: 4]

Chlorine gas is manufactured by the electrolysis of brine using a diaphragm cell.

(a)

Chlorine reacts with aqueous sodium hydroxide in two different ways, depending on the conditions used. In each case, water, sodium chloride and one other chlorine-containing compound are formed.

For each condition below, give the formula of the other chlorine-containing compound and state the oxidation number of chlorine in it.

[ 4 ]

[Maximum number: 1]

Hot aqueous sodium hydroxide reacts with chlorine.

6 \mathrm{NaOH}(\mathrm{aq})+3 \mathrm{Cl}_{2}(\mathrm{~g}) \rightarrow 5 \mathrm{NaCl}(\mathrm{aq})+\mathrm{NaClO}_{3}(\mathrm{aq})+3 \mathrm{H}_{2} \mathrm{O}(\mathrm{l})

Which statement is correct?

The oxidation numbers of chlorine and hydrogen both change in the reaction.

The oxidation numbers of chlorine in the products are -1 and +1 .

If the aqueous sodium hydroxide is cold the reaction produces NaClO instead of $\mathrm{NaClO}_{3}$ .

Sodium undergoes disproportionation in this reaction.

[Maximum number: 1]

The elements in Group 17 of the Periodic Table are called the halogens. They form stable compounds with both metals and non-metals.

The table gives some data about $\mathrm{F}_{2}, \mathrm{HCl}$ and $\mathrm{CaF}_{2}$ .

(a)

HOF is the only known molecule that contains only the elements hydrogen, oxygen and fluorine.

[ 1 ]

(i)

HOF can be made by the reaction of $\mathrm{F}_{2}$ with ice at $-40^{\circ} \mathrm{C}$ . The reaction is similar to the reaction of $\mathrm{Cl}_{2}$ with cold water.

Suggest an equation for the reaction of $F_{2}$ with ice.

[ 1 ]

(a)

(i)

Write an equation for the reaction between chlorine and water.

[ 1 ]