Pearson Edexcel International GCSE (9–1) · CHEMISTRY · Unit
Physical Chemistry
442 practice questions
Topics covered
Practice questions
21–30 of 71 · Hard
Question 21
2 marks · Hard
Answer and see the solution →Explain why a reaction mixture containing marble chips and dilute hydrochloric acid will still have some marble chips left at the end of the experiment.
Question 22
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 23
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 24
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.
Question 25
2 marks · Hard
Answer and see the solution →A student investigates the reaction between magnesium and dilute hydrochloric acid. She uses two samples of magnesium of identical mass: one as a single strip and the other cut into many tiny pieces. State and explain how the rate of reaction will differ between the two samples.
Question 26
5 marks · Hard
Answer and see the solution →A student conducts an experiment to discover how changing the surface area of a solid affects the rate of its reaction with a liquid. She reacts 4.0 g of zinc with 25 cm³ of excess dilute sulfuric acid. She performs the same reaction twice:
(a)[2 marks]Describe a safe method she could use to compare the reaction rate using zinc granules and zinc powder, and state a measurement that would provide evidence for which reaction is faster.
(b)[2 marks]Explain, in terms of particle collisions, why the reaction rate changes when using zinc powder instead of granules.
(c)[1 mark]Suggest one other variable, apart from surface area, that must be kept the same to ensure a fair comparison.
Question 27
2 marks · Hard
Answer and see the solution →Explain, using collision theory, why a powdered solid reacts more quickly with a liquid than the same mass of solid in one lump.
Question 28
2 marks · Hard
Answer and see the solution →A student investigates the reaction between calcium carbonate and hydrochloric acid. State, with a reason, what happens to the rate of reaction if the concentration of hydrochloric acid is reduced to a third, assuming all other conditions remain the same.
Question 29
5 marks · Hard
Answer and see the solution →A student prepares dilute hydrochloric acid for a reaction by adding water to a known volume of 2.50 mol/dm³ hydrochloric acid. She then uses the solution to react with marble chips.
(a)[2 marks]She mixes 10.0 cm³ of 2.50 mol/dm³ acid with 30.0 cm³ of water to make 40.0 cm³ of solution. Calculate the concentration, in mol/dm³, of the hydrochloric acid after dilution.
(b)[2 marks]She repeats the process, using 25.0 cm³ of 2.50 mol/dm³ acid topped up with water to 40.0 cm³. Calculate the new concentration, in mol/dm³, after dilution.
(c)[1 mark]State the formula used to calculate the final concentration when diluting a solution.
Question 30
2 marks · Hard
Answer and see the solution →An experiment produced 0.46 g of carbon dioxide in the first 20 seconds during the reaction of marble chips with dilute hydrochloric acid. Calculate the average rate of carbon dioxide production, giving your answer in g/s. Show your working.