Sometimes the pH must be converted into the hydronium ion concentration. The quickest way to find the hydronium ion concentration in a solution is to use a pH meter to measure the pH and then calculate [H₃O⁺] from the pH. What is the molar concentration of hydronium ions in a solution with pH = 4.83?

ANTICIPATE Because the pH is less than 7, the pH of pure water at 25 °C, the solution must be acidic and you should expect a concentration of H3O1 ions greater than 10^–7 mol · L^–1.

PLAN To calculate the precise value from Eq. 2, first change the sign of the pH and then take its antilogarithm.

[HO+] 10 PH mol-L-1 = (2)