Calculate pH of a 500 ml solution containing 0.6 grams sodium hydroxide (NaOH).

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 sodium hydroxide = 40.0 g/ mole.
Volume of solution in liters = 500 ml/ (1000 ml/ liter) = 0.5 liter.

Number of moles = 0.6 g / (40.0 g/ mole) = 0.015 mole.

Molar concentration = 0.015 mole/ (0.5 liter) = 0.03 M.

Step 2. Calculate pH using molar concentration.

pOH = - log [OH^-]

pOH = - log 0.03 = 1.52

pH + pOH = 14.00

pH = 14.00 - pOH = 14.00 - 1.52 = 12.48

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