Question

pH of \(10^{-3}\) M solution of KOH is

• A. 7.01
• B. 2
• C. 11
• D. 9

Hint:

For strong bases like KOH, the concentration of \(OH^-\) ions equals the concentration of the base. Use this to calculate the pOH and then determine the pH.

Answer 1

The Correct Option is C

KOH is a strong base, so it dissociates completely in water: \[ \text{KOH} \rightarrow \text{K}^+ + \text{OH}^- \] The concentration of \(OH^-\) ions will be equal to the concentration of KOH, which is \(10^{-3}\) M. The pOH is given by: \[ \text{pOH} = -\log[\text{OH}^-] \] Substitute the concentration: \[ \text{pOH} = -\log(10^{-3}) = 3 \] Since: \[ \text{pH} + \text{pOH} = 14 \] \[ \text{pH} = 14 - 3 = 11 \] Thus, the pH of the solution is 11.