O-LevelChemistryChemistry of the Environment5070/22 · May/June 2020 · Q910 Marks

Sulfur dioxide is a colourless gas which can be found in air.

(a)State one environmental problem caused by the presence of sulfur dioxide in air.[1]
(b)When heated in air iron pyrite, FeS2, reacts with oxygen. Sulfur dioxide and iron(III) oxide, Fe2O3, are the products of this reaction. Construct the equation for this reaction.[2]
(c)Give one use for sulfur dioxide.[1]
(d)Liquid sulfur dioxide is stored in cylinders. When the cylinder is opened the liquid quickly changes into a gas. Use the kinetic particle theory to describe the changes in movement and arrangement of the particles when liquid sulfur dioxide becomes a gas.[2]
(e)Sulfur dioxide has a low melting point. Suggest, in terms of structure and bonding, why sulfur dioxide has a low melting point.[2]
(f)Describe the chemical test for sulfur dioxide. test ................................................................................................................................................................................................... observation .................................................................................................................................................................................... [2][2]

Mark scheme

Marking points from the official mark scheme (May/June 2020). The mark or mark type is shown in brackets.

[1] 9(a) acid rain / one effect of acid rain e.g. acidification of lakes or killing trees etc. (1)
[1] 9(b) correct formulae for reactants and products 4FeS2 + 11O2 → 2Fe2O3 + 8SO2 (1)
[1] 9(b) balanced - dependent on correct formulae for reactants and products (1)
[1] 9(c) food preservation / antioxidant / making sulfuric acid / bleaching wood pulp (1)
[1] 9(d) movement – particles move faster (1)
[1] 9(d) arrangement – particles spread out / particles no longer touching each other (1)
[1] 9(e) has a simple (molecular) structure (1)
[1] 9(e) weak intermolecular forces / weak attraction between molecules (1)
[1] 9(f) test - (filter paper dipped in) acidified potassium manganate(VII) (1)
[1] 9(f) observation goes from purple to colourless (1)

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