A solution has pH 3. If the hydrogen-ion concentration becomes one hundred times lower, what will be the approximate new pH?
Answer and explanation
Correct answer: Five
Use the definition pH = −log[H+]. If the hydrogen-ion concentration decreases by a factor of 100, that is a decrease of 10², so the pH increases by 2 units. Starting from pH 3, the new value is 3 + 2 = 5. Therefore option B is correct. A decrease in hydrogen-ion concentration cannot lower the pH to 1, while the other listed values imply a much larger change.
Frequently asked questions
What is the correct answer to this question?
Five
Why is this the correct answer?
Use the definition pH = −log[H+]. If the hydrogen-ion concentration decreases by a factor of 100, that is a decrease of 10², so the pH increases by 2 units. Starting from pH 3, the new value is 3 + 2 = 5. Therefore option B is correct. A decrease in hydrogen-ion concentration cannot lower the pH to 1, while the other listed values imply a much larger 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.
