Question

Find the pH of each of the following solutions of mixtures of acids.

0.100M in HBr and 0.115M in HCHO2

Answer 1

The dissociation of formic acid is as represented below.

Let a M be the change in the concentration of formic acid to reach equilibrium.

	HCOOH
Initial concentration (M)	0.115	0.100	0
Equilibrium concentration (M)	0.115-a	0.100+a	a

The expression for the equilibrium constant K is

Substitute values in the above expression.

This is a quadratic equation with roots -0.100 and .

Since concentration cannot be negative, the value -0.100 is discarded.

Hence,

Hence, the pH of the mixture of HBr and HCOOH is 0.999