A solution has pH 9. Acid is added and the pH becomes 7. What reaction has occurred?
Answer and explanation
Correct answer: Neutralisation
The governing concept is acid-base neutralisation. A pH of 9 indicates that the original solution is basic. Adding acid supplies hydrogen ions, which react with hydroxide ions or other basic species and reduce the basicity. When the pH reaches 7, the solution is approximately neutral under the stated conditions. Therefore option C is correct; displacement, combination, and decomposition are not identified by this pH change.
Frequently asked questions
What is the correct answer to this question?
Neutralisation
Why is this the correct answer?
The governing concept is acid-base neutralisation. A pH of 9 indicates that the original solution is basic. Adding acid supplies hydrogen ions, which react with hydroxide ions or other basic species and reduce the basicity. When the pH reaches 7, the solution is approximately neutral under the stated conditions. Therefore option C is correct; displacement, combination, and decomposition are not identified by this pH change.
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.
