A student has a solution of sodium hydroxide with a pH of 12. The student adds a large volume of water to the solution.
Which statement describes the pH of the solution after the water is added?
The pH increases to above 12, because the alkali is spread through more water.
The pH decreases, but it stays above 7.
The pH decreases to below 7 if enough water is added.
The pH stays at 12, because the amount of sodium hydroxide does not change.
112 exam-style questions on OCR GCSE Chemistry 3.3 Types of chemical reactions, covering 3.3.1 Oxidation and reduction in terms of oxygen, 3.3.2 Acids, alkalis and neutralisation, 3.3.3 The pH scale and measuring pH, 3.3.4 Oxidation and reduction in terms of electrons, 3.3.5 Dilute and concentrated, weak and strong acids, and 3.3.6 Hydrogen ion concentration and pH. Each one has a worked solution and a mark scheme showing where the marks go.