O-LevelChemistryAcids, Bases & Salts5070/21 · Oct/Nov 2016 · Q25 Marks

Sulfuric acid is a strong acid.

(a)(i)What is meant by the term strong acid?[1]
(a)(ii)Describe how you could measure the pH of dilute sulfuric acid.[1]
(b)Many plants cannot grow in soils which are too acidic. Describe and explain how soils which are too acidic can be treated to reduce the acidity.[2]
(c)The graph shows the effect of soil pH on the rate of uptake of potassium ions by plant roots. rate of uptake of potassium ions [Figure with graph showing rate of uptake of potassium ions vs soil pH] Describe how the rate of uptake of potassium ions varies with soil pH.[1]

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Mark scheme

Marking points from the official mark scheme (Oct/Nov 2016). The mark or mark type is shown in brackets.

[1] acid that is completely ionised/acid that is completely dissociated/acid that releases all ionisable hydrogen (1)
[1] add Universal Indicator AND compare colour with pH (colour) chart (1)
[1] add calcium oxide/add lime/add calcium hydroxide/add calcium carbonate (1)
[1] base (reacts with the acid)/neutralising (the acid) (1)
[1] rate increases as pH increases (then remains constant) (1)

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