Sodium hydroxide is a strong base. What is the pH in a 0.01 mol/dm3 solution?
a. pH=2
b. pH=12
c. pH=-2
d. pH=0.01 mol/dm3

b. pH=12

Explanation:

Step 1: Given data

Concentration of NaOH: 0.01 mol/dm³ = 0.01 mol/L = 0.01 M

Step 2: Write the reaction for the dissociation of NaOH

NaOH is a strong base that dissociates according to the following equation.

NaOH(aq) ⇒ Na⁺(aq) + OH⁻(aq)

The molar ratio of NaOH to OH⁻ is 1:1. Then, the concentration of OH⁻ is 0.01 M.

Step 3: Calculate the pOH

pOH = -log [OH⁻] = -log 0.01 = 2

Step 4: Calculate the pH

We will use the following expression.

pH + pOH = 14

pH = 14 - pOH = 14 -2 = 12