The table shows the mass of the product measured at six times during a reversible reaction in a closed flask. At which time was equilibrium first reached?
Table: The mass of the product in a closed flask measured at six times during a reversible reaction
| Time in s | Mass of product in g |
|---|---|
| 0 | 0.00 |
| 20 | 3.20 |
| 40 | 5.10 |
| 60 | 5.80 |
| 80 | 5.80 |
| 100 | 5.80 |
At 20 s20\ \text{s}20 s, because the mass of the product is rising quickly
At 60 s60\ \text{s}60 s, because the mass of the product stops changing
At 80 s80\ \text{s}80 s, because the mass is the same as the mass at 100 s100\ \text{s}100 s
At 100 s100\ \text{s}100 s, because the reaction has had the longest time
40 exam-style questions on AQA GCSE Chemistry 6.2 Reversible reactions and dynamic equilibrium, covering 6.2.1 Reversible reactions, 6.2.2 Energy changes and reversible reactions, 6.2.3 Equilibrium, 6.2.4 The effect of changing conditions on equilibrium, 6.2.5 The effect of changing concentration, 6.2.6 The effect of temperature changes on equilibrium, and 6.2.7 The effect of pressure changes on equilibrium. Each one has a worked solution and a mark scheme showing where the marks go.