pH and indicators

2 marks · Normal

State the colour change observed when litmus paper is placed in (a) an acidic solution and (b) an alkaline solution.

(a)

Colour of litmus paper in an acidic solution:

[1 mark]

(b)

Colour of litmus paper in an alkaline solution:

[1 mark]

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(a) Red

(b) Blue

Common mistakes: Incorrectly swapping colours; Stating 'clear' or 'colourless'

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Marking points

B1 (a) · 1 mark · Correctly states red as the colour in acid.

B1 (b) · 1 mark · Correctly states blue as the colour in alkali.

Worked solution

a) Litmus paper turns red in an acidic solution.

b) Litmus paper turns blue in an alkaline solution.