pH when the coefficient isn't 1
What is the pH of a solution with [H⁺] = 2 × 10⁻⁴ M? (log 2 ≈ 0.3)
Answer B: explanation for every choice
A
This subtracts 0.7, confusing log 2 with ln 2.
B
Correct. pH = −log(2 × 10⁻⁴) = 4 − log 2 = 4 − 0.3 = 3.7.
C
This ignores the coefficient of 2.
D
This adds log 2 instead of subtracting it. More H⁺ means lower pH.
TakeawaypH of a × 10⁻ⁿ = n − log a.
Equation usedpH and pOH
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