CAIE A-Level Chemistry 11 Group 17

Practise halogen property trends, displacement and disproportionation reactions, and hydrogen halide behaviour.

Covered syllabus points

11.1 Physical properties of the Group 17 elements 11.2 The chemical properties of the halogen elements and the hydrogen halides 11.3 Some reactions of the halide ions 11.4 The reactions of chlorine

[Maximum number: 8]

The halogens chlorine, bromine and iodine show trends in chemical and physical properties down the group.

Table 3.1 shows some properties of chlorine, bromine and iodine.

Table 3.1

(a)

Complete Table 3.1.

[ 1 ]

(b)

The bond energy values in Table 3.1 refer to the X-X bond where X is the halogen. Explain the trend in the bond strength of the X-X bond in the halogens.

[ 2 ]

(c)

Explain, with the use of an equation, how chlorine, $\mathrm{Cl}_{2}$ , is used in water purification. State the role of the active species produced.

[ 2 ]

$\mathrm{Cl}_{2}+\mathrm{H}_{2} \mathrm{O} \rightarrow \mathrm{HCl}+\mathrm{HOCl}$

ClO- / HOCl kills bacteria

(d)

The sodium halides in Table 3.1 also show trends in chemical properties.

[ 3 ]

(i)

Identify the sodium halide that reacts with concentrated $\mathrm{H}_{2} \mathrm{SO}_{4}$ to form $\mathrm{H}_{2} \mathrm{~S}$ .

[ 1 ]

(ii)

Identify the sodium halide that only undergoes a Brønsted-Lowry acid-base reaction with concentrated $\mathrm{H}_{2} \mathrm{SO}_{4}$ .

[ 1 ]

(iii)

A student adds a few drops of $\mathrm{AgNO}_{3}(\mathrm{aq})$ to a solution of NaBr(aq). State what is observed.

[ 1 ]

[Maximum number: 5]

Chlorine is one of the elements in Group 17 of the Periodic Table.

(a)

Describe the colours of the Group 17 elements, chlorine to iodine, at room temperature.

[ 1 ]

(b)

Describe the relative reactivity of the elements chlorine to iodine as oxidising agents.

[ 1 ]

(c)

State what is observed when chlorine reacts with hydrogen.

[ 1 ]

(d)

Explain why the thermal stability of the hydrogen halides decreases down the group.

[ 1 ]

(e)

$\mathrm{CHCl}_{3}$ is another halogenoalkane. $\mathrm{CHCl}_{3}$ forms when propanone reacts with NaClO .

NaC 1 O is made from chlorine in a disproportionation reaction.

[ 1 ]

(i)

Identify a reagent and conditions that can be used to convert chlorine to NaC 1 O .

[ 1 ]

[Maximum number: 2]

The chlorides of some of the Period 3 elements are shown in Table 2.1.

Table 2.1

An excess of $\mathrm{Cl}^{-}(\mathrm{aq})$ is added to $1 \mathrm{~cm}^{3}$ of $\mathrm{Br}_{2}(\mathrm{aq})$ .

Describe what is observed. Explain your answer.

M1 orange colour (of solution) remains / no visible reaction

M2

bromine $/ \mathrm{Br}_{2}$ cannot oxidise chloride/Ct

OR

bromine $/ \mathrm{Br}_{2}$ is not a strong enough oxidising agent (to oxidise chloride/Cl-)

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Covered syllabus points

11. Group 17 question 1

Question (a)

Question (b)

Question (c)

Question (d)

Question (i)

Question (ii)

Question (iii)

11. Group 17 question 2

Question (a)

Question (b)

Question (c)

Question (d)

Question (e)

Question (i)

11. Group 17 question 3