If equal volumes of an acid and a base are mixed but the pH does not become 7, what could be a possible reason?
Answer and explanation
Correct answer: Their concentration or strength was not the same
Equal volume does not mean equal chemical amount. Neutralisation depends on the number of reacting H⁺ and OH⁻ ions, which is determined by concentration and acid or base strength. For example, equal volumes of 0.1 M HCl and 0.1 M NaOH can approach pH 7, but unequal concentrations or a weak reactant can leave an excess of one ion. Therefore A is correct.
Frequently asked questions
What is the correct answer to this question?
Their concentration or strength was not the same
Why is this the correct answer?
Equal volume does not mean equal chemical amount. Neutralisation depends on the number of reacting H⁺ and OH⁻ ions, which is determined by concentration and acid or base strength. For example, equal volumes of 0.1 M HCl and 0.1 M NaOH can approach pH 7, but unequal concentrations or a weak reactant can leave an excess of one ion. Therefore 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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