A solution of 1 g/dm 3. hydrochloric acid has a pH of 1.6. Predict its pH when it is diluted to 0.1 g/dm 3. The hydrogen ion concentration decreases by a factor of 10, so the pH increases by 1 ...

The more concentrated the solution of an acid, the lower its pH will be. If the hydrogen ion concentration in a solution increases by a factor of 10, the pH of the solution decreases by 1 unit.