CAIE A Level Chemistry 9701 · Group 2
A student adds a sample of magnesium hydroxide to water and to dilute sulfuric acid. In water, almost none of the solid dissolves. In dilute sulfuric acid, the solid reacts and dissolves. Explain these observations, and write the equation for the reaction with sulfuric acid.
6 marks, so the mark scheme is looking for about 6 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.