Question

Calculate the ph of 0.02 M Hcl​

Answer 1

Since HCl is a strong acid it completely dissociates.

Therefore all the H+ protonates water molecules to give H3O+.

Its concentration here is high enough to ignore H3O+ contribution from water so the pH is just -log(0.02) = 1.7. pH + pOH = 14 so the pOH is 12.3.

The pH is -Log[H+] for HCl - being a strong acid.