Pearson Edexcel International GCSE (9–1) · CHEMISTRY · Section
Changing the concentration of the reactants
19 practice questions
Practice questions
11–19 of 19
Question 11
3 marks · Normal
Answer and see the solution →In an experiment, a student finds that 0.21 g of carbon dioxide are released in the first 30 seconds of a reaction between marble chips and hydrochloric acid. Calculate the average rate of reaction (in g/s) during this time. Show your working.
Question 12
3 marks · Normal
Answer and see the solution →Explain how you can tell from a graph whether the rate of reaction is directly proportional to the concentration of the reactant.
Question 13
4 marks · Normal
Answer and see the solution →The table below gives the concentration of a reactant and the corresponding average rate of reaction measured at the start of an experiment.
Concentration of reactant and average rate Concentration of HCl (mol/dm³) Average rate (g/s) 0.50 0.004 1.00 0.008 1.50 0.012 2.00 0.016 (a)[1 mark]Describe the pattern shown by the data.
(b)[1 mark]Predict the average rate if the concentration is increased to 2.50 mol/dm³.
(c)[2 marks]Explain your answer to part b.
Question 14
1 mark · Normal
Answer and check →Which of the following is the concentration (in mol/dm³) of a solution made by mixing 6.0 cm³ of 2.00 mol/dm³ hydrochloric acid with 19.0 cm³ of distilled water to make a total of 25.0 cm³?
- A.0.30 mol/dm³
- B.0.40 mol/dm³
- C.0.48 mol/dm³
- D.0.60 mol/dm³
Question 15
2 marks · Normal
Answer and see the solution →A reaction between powdered magnesium and dilute hydrochloric acid releases 0.30 g of hydrogen in the first 20 seconds. Calculate the average rate of production of hydrogen gas in g/s.
Question 16
4 marks · Normal
Answer and see the solution →Look at the following graph, which shows the rate of reaction (y-axis, in g/s) against concentration of hydrochloric acid (x-axis, in mol/dm³) for a certain reaction.
Rate of reaction vs concentration of HCl (a)[1 mark]Describe the shape and position of the line on the graph.
(b)[1 mark]What does this show about the relationship between the concentration of hydrochloric acid and the rate of reaction?
(c)[2 marks]If the concentration is doubled, what happens to the rate of reaction? Explain your answer.
Question 17
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 18
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 19
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.