A little base is added to an acidic solution, so pH increases but complete neutralisation does not occur. Why?
Answer and explanation
Correct answer: Not all hydrogen ions have been neutralised
The governing concept is neutralisation and the pH scale. A base supplies hydroxide ions, which react with hydrogen ions from the acid: H⁺ + OH⁻ → H₂O. If only a small amount of base is added, it consumes only part of the available H⁺ ions. Their concentration therefore decreases and pH rises, but some acidity remains, so complete neutralisation has not occurred. Hence option A is correct.
Frequently asked questions
What is the correct answer to this question?
Not all hydrogen ions have been neutralised
Why is this the correct answer?
The governing concept is neutralisation and the pH scale. A base supplies hydroxide ions, which react with hydrogen ions from the acid: H⁺ + OH⁻ → H₂O. If only a small amount of base is added, it consumes only part of the available H⁺ ions. Their concentration therefore decreases and pH rises, but some acidity remains, so complete neutralisation has not occurred. Hence 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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