Why does the solution become warm when acid is added to water?
Answer and explanation
Correct answer: Because the dissolving process releases heat
The governing concept is exothermic dilution. When many concentrated, especially strong, acids dissolve and ionise in water, hydration of the ions releases energy as heat. This increases the temperature of the solution. The warming is not caused by freezing, conversion of acid into a metal, or burning litmus; none of those processes explains ordinary acid dilution. Because the released heat can cause splashing, acid should be added slowly to water with stirring, never water rapidly into concentrated acid. Option A is correct.
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What is the correct answer to this question?
Because the dissolving process releases heat
Why is this the correct answer?
The governing concept is exothermic dilution. When many concentrated, especially strong, acids dissolve and ionise in water, hydration of the ions releases energy as heat. This increases the temperature of the solution. The warming is not caused by freezing, conversion of acid into a metal, or burning litmus; none of those processes explains ordinary acid dilution. Because the released heat can cause splashing, acid should be added slowly to water with stirring, never water rapidly into concentrated acid. Option A is correct.
Which subject and chapter does this question cover?
This is a Class 10 Science question. Chapter: Chemical Substances – Nature and Behaviour. Topic: Acids, Bases, and Salts.
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