Question

1. Harry is a farmer. The soil on his field is too acidic to grow some crops.
a) Harry wants to find out the pH of the soil. He uses litmus.
i) How does litmus tell Harry that the soil is acidic? [1]
ii) Harry’s friend suggested that he uses universal indicator instead of litmus.
Explain why? [1]
b) Harry adds an alkali to the field. The acid in the soil reacts with the alkali. What is the name of this type of reaction? Explain. [2]

Answer 1

Answer:

i) when red litmus paper turns blue it is a base and when blue litmus paper turns red it is acid...

so Hari knows the soil is acidic.

ii) Because universal indicator can turn a range of different colours, it is helpful in specifying the strength of an acid or alkali. As a result, it gives a more precise result than litmus paper, which only tells you if a solution is an acid or base.

iii)Neutralisation involves an acid reacting with a base or an alkali, forming a salt and water.

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