Pearson Edexcel International GCSE (9–1) · CHEMISTRY · Section
Explaining what's happening
19 practice questions
Practice questions
1–8 of 8 · Normal
Question 1
2 marks · Normal
Answer and see the solution →Explain why not every collision between reactant particles in a chemical reaction leads to a reaction.
Question 2
4 marks · Normal
Answer and see the solution →A student adds excess powdered magnesium to dilute hydrochloric acid in a beaker. The mixture fizzes and gives off a gas.
(a)[1 mark]State the name of the gas produced in this reaction.
(b)[3 marks]Explain, using collision theory, why the reaction is faster at the start than near the end.
Question 3
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 4
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 5
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 6
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 7
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 8
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.