What is the pH of a solution that contains 25 grams of hydrochloric acid (hcl) dissolved in 1.5 liters of water?

First we calculate the concentration of HCl:

Moles = mass / Mr

= 25 / 36.5

= 0.685 mol

Concentration = 0.685/1.5 = 0.457 mol / dm³

For a strong monoprotic acid, the concentration of hydrogen ions is equal to the acid concentration.

pH = - log[H+]

pH = - log (0.457)

= 0.34