What is pH of a 1 liter solution containing 0.5 grams of potassium hydroxide (KOH)?

Solution:

Step 1. Calculate molar concentration.

Molar concentration = number of moles/ volume in liters

Number of moles = mass/ molar mass

Molar mass (molecular weight) of potassium hydroxide = 56.1 g/ mole.

Number of moles = 0.5 g / (56.1 g/ mole) = 0.00891 mole.

Molar concentration = 0.00891 mole/ (1 liter) = 0.00891 M.

Step 2. Calculate pH using molar concentration.

pOH = - log [OH^-]

pOH = - log 0.00891 = 2.05

pH + pOH = 14.00

pH = 14.00 - pOH = 14.00 - 2.05 = 11.95

Related posts:
Online pH calculator.
What is an acid? what is a base?