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CAIE A-Level Chemistry AS 11.1 Physical Properties of the Group 17 Elements Questions

Practise describing halogen colour, physical state and volatility trends and explaining them using molecular forces.

Syllabus
2028–2030
Course
Chemistry 9701
Level
AS

Exam points

  • recall the colours and physical states of chlorine, bromine and iodine at room conditions
  • explain decreasing volatility down the group through stronger London forces between larger molecules
  • explain the general weakening of X–X bonds through longer bonds and reduced orbital overlap

Covered syllabus points

11.1.1—Colours and the trend in volatility11.1.2—Trend in the bond strength of the halogen11.1.3—The volatility of the elements

Question 1

[Maximum number: 3]

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

Table 3.1

Question (a)

(a)

Complete Table 3.1.

[ 1 ]

Question (b)

(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 ]

Question 2

[Maximum number: 2]

The Group 17 elements are oxidising agents.

Cl2\mathrm{Cl}_{2} and Br2\mathrm{Br}_{2} can each react with NH3\mathrm{NH}_{3} to give N2\mathrm{N}_{2} and a hydrogen halide, HX .

3X2+2NH3→ N2+6HX3 \mathrm{X}_{2}+2 \mathrm{NH}_{3} \rightarrow \mathrm{~N}_{2}+6 \mathrm{HX}

X = Cl or Br

The relative bond strengths of X-X and H-X determine the difference in enthalpy change of the two reactions.

Describe and explain the difference in the X-X bond strengths of Cl2\mathrm{Cl}_{2} and Br2\mathrm{Br}_{2}.

Question 3

[Maximum number: 3]

The halogens chlorine, bromine and iodine are all volatile elements.

State and explain the trend in volatility down Group 17.

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