Question

What is the pH of a solution containing 0.383
mol L^-1 CH₃COOH and 0.392 CH₃COO^- mol L^-1 ? Round your answer to 2 decimal places.

Answer 1

The reaction is given by

0.383 M 0.392M 0M Initial Concentration

      Change

0.383 0.392    Equilibrium Concentration

.... eq (1)

Since   is a weak acid therfore it dissociates very weakly .So

Therefore,

  

of acetic acid is

and

Therefore,

Note- this is only an approximate value of pH.For a more accurate value the equation (1) is solved (quadratic equation which gives two values of x . One of which could be absurd and can be ignored ).Though an approximation has been used still the value of x and hence pH would very nearly be the same