A basic solution changes from pH 14 to pH 11. Approximately how did its basicity change?
Answer and explanation
Correct answer: Decreased one thousand times
The pH scale is logarithmic, so a three-unit decrease corresponds to a factor of 10³ in hydrogen-ion concentration. For basicity, the relevant hydroxide-ion concentration changes oppositely: pH 14 corresponds to pOH 0, while pH 11 corresponds to pOH 3. Thus [OH⁻] falls from about 1 M to 10⁻³ M, a thousandfold decrease. The solution remains basic, but much less strongly basic; A is correct.
Frequently asked questions
What is the correct answer to this question?
Decreased one thousand times
Why is this the correct answer?
The pH scale is logarithmic, so a three-unit decrease corresponds to a factor of 10³ in hydrogen-ion concentration. For basicity, the relevant hydroxide-ion concentration changes oppositely: pH 14 corresponds to pOH 0, while pH 11 corresponds to pOH 3. Thus [OH⁻] falls from about 1 M to 10⁻³ M, a thousandfold decrease. The solution remains basic, but much less strongly basic; 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.
