Pearson Edexcel International GCSE (9–1) · CHEMISTRY · Unit
Physical Chemistry
442 practice questions
Topics covered
Practice questions
121–130 of 188 · Normal
Question 121
3 marks · Normal
Answer and see the solution →Some students write the following equation:
Explain how you could tell whether this reaction is reversible or not, using the chemical symbols and the reaction itself.
Question 122
4 marks · Normal
Answer and see the solution →The table shows the concentration of hydrogen, iodine and hydrogen iodide in a sealed container at different times during a reversible reaction.
Time (min) [H2] (mol dm⁻³) [I2] (mol dm⁻³) [HI] (mol dm⁻³) 0 0.50 0.50 0.00 1 0.30 0.30 0.40 2 0.21 0.19 0.60 3 0.19 0.18 0.64 4 0.18 0.17 0.65 5 0.18 0.17 0.65 Use the data to answer the following questions.
(a)[2 marks]At what time does the reaction reach dynamic equilibrium? Explain how you know.
(b)[1 mark]State one characteristic of the reaction mixture at equilibrium based on the data.
(c)[1 mark]Suggest what would happen if more H2 is added at equilibrium.
Question 123
2 marks · Normal
Answer and see the solution →Ammonium chloride can decompose when heated to form ammonia and hydrogen chloride. The reaction is reversible.
Write a balanced chemical equation for this reaction, including the correct symbol for reversibility, and name one characteristic of a reversible reaction.
Question 124
4 marks · Normal
Answer and see the solution →The reversible decomposition of dinitrogen tetroxide to nitrogen dioxide is shown below:
(a)[2 marks]Explain what is meant by 'dynamic' in dynamic equilibrium.
(b)[2 marks]Describe what you would observe in the sealed container when equilibrium has been reached.
Question 125
1 mark · Normal
Answer and check →Which statement correctly describes the characteristics of a reaction at dynamic equilibrium in a sealed container?
- A.The forward reaction has stopped, but the reverse reaction continues.
- B.The concentrations of reactants and products do not change because both reactions have stopped.
- C.The forward and reverse reactions continue at the same rate, and concentrations of all substances stay constant.
- D.The amount of reactants decreases steadily until only products remain.
Question 126
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 127
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 128
3 marks · Normal
Answer and see the solution →Explain, with reasons, why a sealed container is necessary for studying reversible reactions.
Question 129
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.
Question 130
1 mark · Normal
Answer and check →Which process below best describes the decomposition of ammonium chloride, when heated in a sealed container?
- A.NH4Cl(s) breaks down into NH3(g) and HCl(g), which cannot escape and can recombine to form NH4Cl(s).
- B.NH4Cl(s) melts into a liquid and cannot return to solid form.
- C.NH4Cl(s) reacts with oxygen to form water and nitrogen gas.
- D.NH4Cl(s) changes into NH3(g) and HCl(g), which leave the container permanently.