If the ka of a monoprotic weak acid is 5.1 × 10-6, what is the ph of a 0.18 m solution of this acid?

Hello!

The dissociation reaction of a monoprotic weak acid is the following:

HA + H₂O ⇄ A⁻ + H₃O⁺

The ka value is expressed as follows:



After the dissociation, we can clear for the concentration of H₃O⁺ (x) in the following way (Considering that x is small).



So, to finish, we apply the definition of pH



So the pH of this solution is 3,02

Have a nice day!