Pearson Edexcel International GCSE (9–1) · CHEMISTRY · Section
Explaining what's happening
19 practice questions
Practice questions
11–19 of 19
Question 11
3 marks · Normal
Answer and see the solution →A student investigates the reaction between sodium thiosulfate and hydrochloric acid at two different temperatures. The reaction is much faster at 45°C than at 25°C. Explain, using collision theory, why increasing the temperature increases the rate of this reaction.
Question 12
4 marks · Normal
Answer and see the solution →The graph below shows the concentration of hydrochloric acid over time during its reaction with excess calcium carbonate.
Concentration of hydrochloric acid vs time (a)[2 marks]Describe how the rate of reaction changes during the experiment.
(b)[2 marks]Explain the shape of the curve using collision theory.
Question 13
1 mark · Normal
Answer and check →Which statement best explains why a reaction only occurs when particles collide with at least the activation energy?
- A.It allows more particles to react with each other at low temperatures.
- B.It provides enough energy to break existing bonds for the reaction to occur.
- C.It increases the frequency of collisions between reactant particles.
- D.It makes the product more stable after the reaction.
Question 14
2 marks · Normal
Answer and see the solution →State the two conditions that must be met for a collision between reactant particles to lead to a reaction, according to collision theory.
Question 15
4 marks · Normal
Answer and see the solution →A reaction between excess zinc and dilute sulfuric acid is carried out in a conical flask. The total volume of hydrogen gas produced is measured.
(a)[1 mark]State one way the rate of this reaction could be increased without changing the temperature.
(b)[3 marks]Explain your answer to part (a) using collision theory.
Question 16
3 marks · Normal
Answer and see the solution →A student reacts marble chips (calcium carbonate) with dilute hydrochloric acid in a beaker. At the start, there are 60 acid particles per cm³ in the solution. Every second, about 18 of these particles collide with the marble chips. Only 5 of these collisions have enough energy to result in a reaction and are called successful collisions.
(a)[2 marks]Calculate the percentage of collisions that are successful each second at the start of the reaction.
(b)[1 mark]Explain, using collision theory, what happens to the rate of reaction as the number of acid particles falls during the experiment.
Question 17
2 marks · Hard
Answer and see the solution →The reaction between excess potassium carbonate and dilute nitric acid is observed to slow down over time. Explain, using collision theory, why this happens.
Question 18
5 marks · Hard
Answer and see the solution →A student compares the rates of reaction between two samples of marble chips (calcium carbonate) and dilute phosphoric acid at room temperature. In experiment 1, large marble chips are used; in experiment 2, the marble chips are crushed into a fine powder. The same mass of marble and the same volume of acid are used in both experiments.
(a)[2 marks]State which experiment will have the faster initial rate of reaction, and give a reason using collision theory.
(b)[1 mark]Draw a suitable diagram to show the difference in surface area between the marble chips in experiment 1 and the powder in experiment 2.
(c)[2 marks]Explain, using collision theory, why the reaction stops even though there is excess marble in both experiments.
Question 19
2 marks · Hard
Answer and see the solution →A sealed flask contains hydrogen peroxide decomposing into water and oxygen gas. The reaction rate decreases over time. Use collision theory to explain why the rate gets slower, even though the temperature stays the same.