CAIE A Level Chemistry 9701 · Equilibria
In the blood, carbon dioxide dissolves and reacts with water to form carbonic acid, , which partially dissociates:
(a) Identify the conjugate acid–base pair in this equilibrium.
(b) Explain how this equilibrium helps to control the pH of blood when the concentration of increases.
5 marks, so the mark scheme is looking for about 5 separate creditworthy points. Making the same point twice in different words earns it once.
Explain means: Give the reasons or the mechanism: why or how something happens. Link each point to the next with because, so or which means. A list of facts with no links usually loses the reasoning marks.
Written by Markquill to follow the Cambridge International syllabus. Markquill is independent and is not affiliated with or endorsed by Cambridge International.