What is the pH of 10⁻3 mol/dm³ hydrochloric acid (a strong monobasic acid)?
Answer and explanation
Correct answer: B. 3
- Step 1: HCl is fully ionised, so [H⁺] = 10⁻3 mol/dm³. Step 2. pH = −log₁₀(10⁻3) = 3. Answer: 3. Why not the others: 11 is what you get if you give the pOH. -3 is what you get if you forget the minus sign in pH = −log[H⁺]. 10 is what you get if you add 7.
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