Calculate the pH of a solution prepared by dissolving 0.15 mol benzoic acid (C7H5O2H) and 0.30 mol of sodium benzoate (Na C7H5O2) in water sufficient to yield 1.00 L of solution. The Ka of benzoic acid is 6.50 x 10-5

Answer : The pH of a solution is, 4.5

Explanation : Given,

Moles of benzoic acid = 0.15 mol

Moles of sodium benzoate = 0.30 mol

Volume of solution = 1.00 L

The dissociation constant for benzoic acid =

First we have to calculate the value of .

The expression used for the calculation of is,

Now put the value of in this expression, we get:

Now we have to calculate the pH of a solution.

Using Henderson Hesselbach equation :

Now put all the given values in this expression, we get:

Therefore, the pH of a solution is, 4.5