Chemistry

Chemistry

Problem

A sodium hydroxide solution at 25 °C has a measured pOH of 3.60. Determine the molarity of NaOH in the solution.
Intuitive explanation

The key is recognizing that pOH directly tells you the concentration of hydroxide ions, which equals the NaOH molarity since NaOH completely dissociates in water. Use the relationship pOH=−log⁡[OH−]\text{pOH} = -\log[\text{OH}^-] to reverse-engineer the [OH−][\text{OH}^-] concentration, then remember that one NaOH molecule produces exactly one OH−\text{OH}^- ion, so the molarity of the base equals the molarity of hydroxide.

Intuitive explanation

The key is recognizing that pOH directly tells you the concentration of hydroxide ions, which equals the NaOH molarity since NaOH completely dissociates in water. Use the relationship pOH=−log⁡[OH−]\text{pOH} = -\log[\text{OH}^-] to reverse-engineer the [OH−][\text{OH}^-] concentration, then remember that one NaOH molecule produces exactly one OH−\text{OH}^- ion, so the molarity of the base equals the molarity of hydroxide.

Browse the problem library