An acidic solution has pH 2. If it is made ten thousand times less acidic, what will be the approximate new pH?
Answer and explanation
Correct answer: Six
The governing relationship is pH = −log[H⁺]. A tenfold decrease in hydrogen-ion concentration raises pH by one unit. Ten thousand equals 10⁴, so making the solution 10,000 times less acidic means [H⁺] decreases by four powers of ten and pH rises by four units. Starting from pH 2: 2 + 4 = 6. Thus option B is correct. This assumes the stated change refers to hydrogen-ion concentration and ignores minor water-ion effects.
Frequently asked questions
What is the correct answer to this question?
Six
Why is this the correct answer?
The governing relationship is pH = −log[H⁺]. A tenfold decrease in hydrogen-ion concentration raises pH by one unit. Ten thousand equals 10⁴, so making the solution 10,000 times less acidic means [H⁺] decreases by four powers of ten and pH rises by four units. Starting from pH 2: 2 + 4 = 6. Thus option B is correct. This assumes the stated change refers to hydrogen-ion concentration and ignores minor water-ion effects.
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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