When acid is added to a solution, its pH goes below 7. Which ion has become relatively more abundant?
Answer and explanation
Correct answer: Hydrogen ion
The governing concept is the pH scale and its relation to hydrogen-ion concentration. A pH below 7 indicates an acidic solution, which means the effective concentration of hydrogen ions, often represented as H+ or hydronium ions H3O+, has increased relative to hydroxide ions. Adding acid therefore shifts the ion balance toward hydrogen ions. Calcium and sodium ions are not the defining cause of acidity, while increased hydroxide ions would indicate a basic tendency. Option A is correct.
Frequently asked questions
What is the correct answer to this question?
Hydrogen ion
Why is this the correct answer?
The governing concept is the pH scale and its relation to hydrogen-ion concentration. A pH below 7 indicates an acidic solution, which means the effective concentration of hydrogen ions, often represented as H+ or hydronium ions H3O+, has increased relative to hydroxide ions. Adding acid therefore shifts the ion balance toward hydrogen ions. Calcium and sodium ions are not the defining cause of acidity, while increased hydroxide ions would indicate a basic tendency. 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.
