Gases A, B and C react reversibly in a sealed vessel at constant temperature.
A(g)+B(g)⇌C(g) \mathrm{A(g) + B(g) \rightleftharpoons C(g)} A(g)+B(g)⇌C(g)The table shows the amount of C at two times.
| Time in minutes | Amount of C in mol |
|---|---|
| 3 | 0.18 |
| 7 | 0.30 |
What explains the change in the amount of C between 3 minutes and 7 minutes?
The forward and reverse rates are equal because A and B react in a 1:1 ratio.
C increases because the reverse reaction changes A and B into C.
More C is made each second than reacts to reform A and B.
The reverse reaction cannot start until the amount of C becomes constant.
124 exam-style questions on OCR GCSE Chemistry 5.3 Equilibria, covering 5.3.1 Reversible reactions and dynamic equilibrium and 5.3.2 Changing the position of equilibrium. Each one has a worked solution and a mark scheme showing where the marks go.