Pearson Edexcel International GCSE (9–1) · CHEMISTRY · Chapter
Reversible Reactions and Equilibria
144 practice questions
Topics covered
- Reversibility and dynamic equilibria19 practice questions
- Reversible reactions in a sealed container18 practice questions
- The position of equilibrium20 practice questions
- Changing the pressure19 practice questions
- Changing the temperature19 practice questions
- Adding a catalyst19 practice questions
- The effect of concentration19 practice questions
Practice questions
21–30 of 144
Question 21
2 marks · Easy
Answer and see the solution →The thermal decomposition of solid ammonium chloride is a reversible reaction.
Explain why both ammonia and hydrogen chloride gases are observed inside the sealed tube during heating, and why a white solid appears again above the heated area.
Question 22
3 marks · Easy
Answer and see the solution →A student records the number of red and green squares at different times in a sealed container during a reversible reaction.
Time (s) Red squares Green squares 0 40 0 1 30 10 2 23 17 3 19 21 (a)[1 mark]How many total squares are there in the container at each recorded time?
(b)[1 mark]What does this suggest about the system in the container?
(c)[1 mark]State what feature of the container ensures this result in a reversible reaction.
Question 23
1 mark · Easy
Answer and see the solution →State what term is used when the rate of the forward reaction equals the rate of the backward reaction in a sealed system.
Question 24
3 marks · Easy
Answer and see the solution →When heating ammonium chloride in a sealed test tube, a reversible reaction takes place.
(a)[1 mark]Write a chemical equation to show the decomposition of ammonium chloride on heating.
(b)[1 mark]State the names of the products formed during the decomposition.
(c)[1 mark]Give a reason why the reaction is reversible.
Question 25
1 mark · Easy
Answer and see the solution →State the chemical formula of the white solid that forms when ammonia and hydrogen chloride gases react together in a sealed tube.
Question 26
2 marks · Easy
Answer and see the solution →A reversible reaction occurs in a sealed container. At the start, there are 80 blue squares representing reactant molecules. Every second, one fifth of the blue squares turn yellow (product molecules). After one second, how many blue squares remain? Show your calculation.
Question 27
2 marks · Normal
Answer and see the solution →State what is meant by a sealed container in the context of reversible reactions. Give two essential features.
Question 28
4 marks · Normal
Answer and see the solution →A reversible reaction takes place in a sealed flask. At first, only reactants are present. The forward reaction starts quickly, but slows down over time.
(a)[1 mark]Explain why the rate of the forward reaction decreases as the reaction proceeds.
(b)[1 mark]Describe what is happening with the reverse reaction as the products begin to form.
(c)[1 mark]State what is meant by equilibrium in this context.
(d)[1 mark]Explain why equilibrium can only be reached in a sealed container.
Question 29
3 marks · Normal
Answer and see the solution →Explain, with reasons, why a sealed container is necessary for studying reversible reactions.
Question 30
4 marks · Normal
Answer and see the solution →The table shows the number of blue and yellow squares in a sealed container at intervals during a reversible reaction.
Time (s) Number of blue squares Number of yellow squares 0 64 0 1 48 16 2 36 28 3 27 37 4 20 44 (a)[1 mark]Describe the trend in the number of blue squares over time.
(b)[1 mark]Describe how the number of yellow squares changes over time.
(c)[1 mark]Predict what will happen to the numbers of blue and yellow squares if the reaction continues.
(d)[1 mark]Explain how these trends are related to reversible reactions reaching equilibrium.