A small amount of base is added to an acidic solution and pH changes from 3 to 5. How much did the acidity change approximately?
Answer and explanation
Correct answer: Decreased one hundred times
The pH scale is logarithmic, so a rise of one pH unit means that the hydrogen-ion concentration, which represents acidity, decreases by a factor of 10. Here the pH rises from 3 to 5, a change of two units. Therefore, the hydrogen-ion concentration becomes 10 × 10 = 100 times smaller. Thus option A is correct; the other choices ignore the logarithmic nature of pH.
Frequently asked questions
What is the correct answer to this question?
Decreased one hundred times
Why is this the correct answer?
The pH scale is logarithmic, so a rise of one pH unit means that the hydrogen-ion concentration, which represents acidity, decreases by a factor of 10. Here the pH rises from 3 to 5, a change of two units. Therefore, the hydrogen-ion concentration becomes 10 × 10 = 100 times smaller. Thus option A is correct; the other choices ignore the logarithmic nature of pH.
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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