Question

What is the pH of a 0.001 M NaOH solution?

• A. 11
• B. 12
• C. 13
• D. 14

Hint:

For strong bases like NaOH, the pH can be calculated directly from the concentration of hydroxide ions, while for weak bases, equilibrium calculations are needed.

Answer 1

The Correct Option is C

NaOH is a strong base, so it dissociates completely in water. The concentration of \( \text{OH}^- \) ions is equal to the concentration of NaOH, which is 0.001 M. The pOH is given by the equation: \[ \text{pOH} = -\log [\text{OH}^-] \] Substitute the value of \( [\text{OH}^-] = 0.001 \, \text{M} \): \[ \text{pOH} = -\log (0.001) = 3 \] Since \( \text{pH} + \text{pOH} = 14 \), we have: \[ \text{pH} = 14 - 3 = 13 \] Thus, the pH of the NaOH solution is 13.