What is the pH of a 0.025 M solution of KOH at 25 °C?
A) 1.60
B) 3.69
C) 10.31
D) 12.40
The pH of a solution can be calculated by taking the negative logarithm (base 10) of the concentration of hydroxide ions ([OH-]) in the solution.
Since KOH is a strong base, it dissociates completely in water to form KOH(aq) → K+(aq) + OH-(aq).
The concentration of KOH is 0.025 M, so the concentration of OH- is also 0.025 M.
Taking the negative logarithm of 0.025:
pOH = -log(0.025) = 1.60
Since pH + pOH = 14 (at 25 °C), we can calculate pH:
pH = 14 - pOH = 14 - 1.60 = 12.40
Therefore, the pH of the solution is 12.40.
The correct answer is option D) 12.40.