O-LevelChemistryMetals & Reactivity5070/22 · May/June 2023 · Q28 Marks

Group VII includes the elements fluorine, chlorine, bromine and iodine.

(a)Chlorine is a green gas at room temperature and pressure. State the appearance of iodine at room temperature and pressure.[2]
(b)(i)Chlorine reacts with aqueous potassium iodide in a displacement reaction. Cl₂(aq) + 2I⁻(aq) → 2Cl⁻(aq) + I₂(aq) Explain, in terms of electrons, why chlorine is an oxidising agent in this reaction.[1]
(b)(ii)State the oxidation number of iodine in I₂.[1]
(b)(iii)Describe what is observed during the displacement reaction.[1]
(c)(i)The rate of diffusion of fluorine gas is greater than that of chlorine gas under the same conditions of temperature and pressure. State what is meant by the term diffusion.[1]
(c)(ii)Explain why the rate of diffusion of fluorine is greater than that of chlorine under the same conditions.[1]
(c)(iii)The rate of diffusion of fluorine increases as the temperature increases. Suggest why using ideas about kinetic particle theory.[1]

Mark scheme

Marking points from the official mark scheme (May/June 2023). The mark or mark type is shown in brackets.

2(a) Grey-black (1)
solid (1)
2(b)(i) chlorine gains electrons (1)
2(b)(ii) 0 (1)
2(b)(iii) (colourless) to orange / brown (1)
2(c)(i) (net) movement of (any) particles or substance from high concentration to low concentration (1)
2(c)(ii) fluorine has a lower (relative) molecular mass / fluorine molecules have less mass (1)
2(c)(iii) (fluorine) molecules or particles move faster / (fluorine) molecules have more kinetic energy (1)

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