If the concentration of hydrogen ions in an acidic solution increases ten times, what is the general effect on pH?
Answer and explanation
Correct answer: pH decreases by about one unit
The governing relationship is pH = −log₁₀[H⁺]. If the hydrogen-ion concentration changes from [H⁺] to 10[H⁺], the new pH is −log₁₀(10[H⁺]) = −1 − log₁₀[H⁺], which is one unit lower. The solution therefore becomes more acidic. A numerical value cannot be fixed without the starting pH, but the general change is clear. Hence option A is correct.
Frequently asked questions
What is the correct answer to this question?
pH decreases by about one unit
Why is this the correct answer?
The governing relationship is pH = −log₁₀[H⁺]. If the hydrogen-ion concentration changes from [H⁺] to 10[H⁺], the new pH is −log₁₀(10[H⁺]) = −1 − log₁₀[H⁺], which is one unit lower. The solution therefore becomes more acidic. A numerical value cannot be fixed without the starting pH, but the general change is clear. 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.
