Question

What is the pH of a 0.500 M solution of HF (Ka = 6.8 x 10¯4)?

Answer 1

So,

First we need to write the dissociation reaction and check the initial, change, and final concentrations:

Using the fact that the equilibrium constant can be found with the equation:

We know the value for Ka, so, let's replace it and then solve for x:

The value of x represents the H+ ions concentration. Using the definition of pH:

Therefore, the pH of the solution is 1.74.