Acids, Bases and Salts

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Practise O/L exam questions on Acids, Bases and Salts with worked solutions

1. 2021 · Paper II · 6 marks
   A student tests four solutions A, B, C and D with universal indicator. The colours obtained are: A — red (pH 2), B — green (pH 7), C — blue (pH 11), D — orange (pH 4). (i) Identify the acidic, neutral and alkaline solutions. (ii) Write the word equation for the neutralisation reaction between solutions A and C. (iii) Name ONE everyday use of an alkali.
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   (i) Acidic: A (pH 2) and D (pH 4); Neutral: B (pH 7); Alkaline: C (pH 11). (ii) Acid + Alkali → Salt + Water (i.e. hydrochloric acid + sodium hydroxide → sodium chloride + water). (iii) Toothpaste / baking soda for cooking / lime to neutralise acidic soil (any valid example accepted).
   Source: NIE O/L Science 2021 Paper II Q5

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