DP Chemistry (first assessment 2025)
Question 19M.2.SL.TZ2.5b
| Date | May 2019 | Marks available | [Maximum mark: 1] | Reference code | 19M.2.SL.TZ2.5b |
| Level | SL | Paper | 2 | Time zone | TZ2 |
| Command term | State | Question number | b | Adapted from | N/A |
b.
[Maximum mark: 1]
19M.2.SL.TZ2.5b
(b)
When a bottle of carbonated water is opened, these equilibria are disturbed.
State, giving a reason, how a decrease in pressure affects the position of Equilibrium (1).
[1]
Markscheme
shifts to left/reactants AND to increase amount/number of moles/molecules of gas/CO2 (g) [✔]
Note: Accept “shifts to left/reactants AND to increase pressure”.
Examiners report
Many students gave generic responses referring to a correct shift without conveying the idea of compensation or restoration of pressure or moles of gas. This generic reply reflects the difficulty in applying a theoretical concept to the practical situation described in the question.
Syllabus sections
Reactivity 2. How much, how fast and how far? » Reactivity 2.3—How far? The extent of chemical change » Reactivity 2.3.4—Le Châtelier’s principle enables the prediction of the qualitative effects of changes in concentration, temperature and pressure to a system at equilibrium. Apply Le Ch.telier’s principle to predict and explain responses to changes of systems at equilibrium.