The dissociation constant of a substituted benzoic acid at 25°C is 1.0 × 10⁻⁴. The pH of a 0.01 M solution of its sodium salt is :

The sodium salt of benzoic acid is a strong base-weak acid salt and its pH is given as follows:

pH = pKw + pKa + logC/2

Now, pKw = 14
pKa = -logKa = -log(10⁻⁴) = 4
logC = log(0.01) = log(10⁻²) = -2

∴pH = 14 + 4 - 2/2 = 8