Pearson Edexcel International GCSE (9–1) · CHEMISTRY · Section
Explaining what's happening
19 practice questions
Practice questions
1–8 of 8 · Easy
Question 1
1 mark · Easy
Answer and see the solution →State the minimum condition that must be met for a chemical reaction to occur between two particles, according to collision theory.
Question 2
3 marks · Easy
Answer and see the solution →The reaction between powdered iron and dilute sulfuric acid produces hydrogen gas.
(a)[1 mark]State what particles must do for a reaction to take place according to collision theory.
(b)[1 mark]Name the term for the minimum amount of energy particles need to react when they collide.
(c)[1 mark]Explain why the reaction slows down as the acid is gradually used up.
Question 3
2 marks · Easy
Answer and see the solution →Explain, using collision theory, why a reaction between magnesium ribbon and excess hydrochloric acid is faster at the start than at the end.
Question 4
3 marks · Easy
Answer and see the solution →A student observes the reaction between excess sodium carbonate and dilute hydrochloric acid. The table shows the concentration of acid over time.
Concentration of acid during reaction Time (min) Acid concentration (mol/dm³) 0 1.00 1 0.85 2 0.70 3 0.60 4 0.59 5 0.59 (a)[1 mark]Between which two times was the reaction fastest? Explain your answer.
(b)[1 mark]State why the reaction gradually slows down as shown in the table.
(c)[1 mark]According to collision theory, what needs to happen for acid particles to react with sodium carbonate?
Question 5
1 mark · Easy
Answer and see the solution →Name the theory that explains how the frequency and energy of collisions affect the rate of chemical reactions.
Question 6
3 marks · Easy
Answer and see the solution →A student investigates how fast sodium reacts with water to produce hydrogen gas at room temperature.
(a)[1 mark]State what must happen to sodium and water particles for this reaction to occur.
(b)[1 mark]According to collision theory, what is a successful collision?
(c)[1 mark]Explain why the reaction rate might change during the experiment.
Question 7
2 marks · Easy
Answer and see the solution →A reaction in a beaker starts with 50 reacting particles per cm³. After a few minutes, only 10 reacting particles per cm³ remain.
Calculate the percentage decrease in the number of reacting particles per cm³ during the reaction.
Question 8
2 marks · Easy
Answer and see the solution →In a reaction, there are 40 effective collisions per minute at the start. After some time, the number of effective collisions drops to 12 per minute.
Calculate how many times faster the reaction was at the start compared to later. Give your answer as a number.