Equal volumes of an acid and a base are mixed, but pH does not become 7. Which reason is most scientific?
Answer and explanation
Correct answer: Equal volume does not mean equal amount of ions
Neutralisation depends on the stoichiometric amounts of hydrogen and hydroxide ions, not merely on the volumes mixed. Equal volumes can have different concentrations or different strengths, so one reactant may remain in excess. For example, equal volumes of 0.1 M acid and 0.01 M base cannot neutralise completely. The final pH therefore need not be 7. Hence option A is the scientific reason.
Frequently asked questions
What is the correct answer to this question?
Equal volume does not mean equal amount of ions
Why is this the correct answer?
Neutralisation depends on the stoichiometric amounts of hydrogen and hydroxide ions, not merely on the volumes mixed. Equal volumes can have different concentrations or different strengths, so one reactant may remain in excess. For example, equal volumes of 0.1 M acid and 0.01 M base cannot neutralise completely. The final pH therefore need not be 7. Hence option A is the scientific reason.
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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