The ph of a 0.25 m aqueous solution of hydrofluoric acid, hf, at 25.0 °c is 2.03. what is the value of ka for hf?
6.0 × 10-5
3.5 × 10-4
1.1 × 10-9
2.0 × 10-9
none of the above

Answer : The correct option is,

Solution : Given,

pH = 2.03

Concentration of HF = 0.25 M

First we have to calculate the concentration of ion.

Now we have to calculate the value of for HF.

The equilibrium reaction will be

Concentration of = Concentration of =

The expression for for HF will be,

Therefore, the value of for HF is,