The hydrogen ion concentration of a solution is 1.6 x 10-4?mol dm-3. Find the pH of this solution.

The hydrogen ion concentration of a solution of sodium hydroxide is 3.5 x 10-11?mol dm-3. Find the pH of this solution.

Ethanoic acid (also known as acetic acid) is a weak acid produced by wood ants that they can spray at predators as a defence mechanism. The hydrogen ion concentration of a sample of ethanoic acid taken from some wood ants was 8.39 x 10-6?mol dm-3. Find the pH of the ethanoic acid produced by wood ants.

Don’t forget the minus sign in the formula:?pH = -log?? [H?].?This is easy to overlook and is a common mistake that students make in exams. Remember: pH must fall between 0 and 14 so if your answer is outside of this range, something has gone wrong! Also, as seen in worked examples above, the question may give you a clue as to what your answer should roughly be. For example, we know that sodium hydroxide is an alkali, so a pH of 10.5 makes sense and we are told that the ethanoic acid produced by wood ants is a weak acid, so 5.08 makes sense too!