Pearson Edexcel International GCSE (9–1) · CHEMISTRY · Unit
Physical Chemistry
442 practice questions
Topics covered
Practice questions
111–120 of 188 · Normal
Question 111
1 mark · Normal
Answer and check →Which statement best describes how a catalyst speeds up a reaction?
- A.A catalyst increases the total enthalpy change (ΔH) of a reaction.
- B.A catalyst provides an alternative pathway with lower activation energy.
- C.A catalyst makes the products more stable.
- D.A catalyst increases the concentration of reactants.
Question 112
2 marks · Normal
Answer and see the solution →Draw a reaction profile diagram for a reaction with and without a catalyst. Clearly label the energy of reactants, energy of products, activation energy with and without catalyst, and the enthalpy change (ΔH).
Question 113
4 marks · Normal
Answer and see the solution →You want to test whether a black solid is a catalyst for the decomposition of hydrogen peroxide solution.
(a)[2 marks]Describe how you would carry out the experiment to test if the black solid is a catalyst.
(b)[2 marks]Explain how you would show that the black solid is unchanged after the reaction.
Question 114
6 marks · Normal
Answer and see the solution →A student investigates the reaction between zinc granules and dilute hydrochloric acid. She wants to find out how both the surface area of zinc and the concentration of acid affect the rate of reaction.
(a)[1 mark]State what will happen to the rate of reaction if she uses powdered zinc instead of granules, keeping everything else the same.
(b)[2 marks]Explain, in terms of particles and collisions, why your answer in (a) is correct.
(c)[1 mark]Next, she repeats the experiment using the same mass of zinc powder but halves the concentration of hydrochloric acid. Predict how the rate of reaction changes, compared to the experiment with original concentration.
(d)[2 marks]Explain your answer in (c).
Question 115
6 marks · Normal
Answer and see the solution →A chemist prepares a solution by diluting hydrochloric acid with water, then reacts it with iron filings instead of an iron bar.
(a)[2 marks]Explain why the iron filings react faster with hydrochloric acid than a single iron bar, assuming the same mass is used.
(b)[3 marks]The chemist mixes 10.0 cm³ of 2.00 mol/dm³ hydrochloric acid with 15.0 cm³ of distilled water to make a total solution volume of 25.0 cm³.
Calculate the concentration of hydrochloric acid in the diluted solution. Show your working.
(c)[1 mark]State how doubling the concentration of hydrochloric acid (in a different experiment) would affect the rate of reaction with iron filings. Give a reason for your answer.
Question 116
6 marks · Normal
Answer and see the solution →A student compares two reactions:
• Reaction 1: 5.0 g of solid calcium carbonate powder is added to 25.0 cm³ of 2.00 mol/dm³ hydrochloric acid. • Reaction 2: 5.0 g of solid calcium carbonate lumps is used with 25.0 cm³ of 1.00 mol/dm³ hydrochloric acid.
For both experiments, the mass of CO₂ gas given off in the first 30 seconds is recorded.
(a)[2 marks]In Reaction 1, the student finds the mass of CO₂ lost after 30 seconds is 0.36 g. Calculate the average rate of reaction during this time. Give your answer in g/s.
(b)[2 marks]Explain why Reaction 1 is expected to be faster than Reaction 2, using both surface area and concentration in your answer.
(c)[2 marks]In Reaction 2, the student records a mass loss of 0.13 g in the first 30 seconds. Calculate the average rate of reaction for Reaction 2.
Question 117
6 marks · Normal
Answer and see the solution →The graph below shows how the rate of reaction changes with the concentration of hydrochloric acid for two experiments. In both experiments, a different form of magnesium is reacted with hydrochloric acid at 20°C. Experiment A uses magnesium ribbon cut into strips; Experiment B uses powdered magnesium. All other conditions are the same.
Rate of reaction (y-axis) vs concentration of HCl (x-axis), two lines: A (strips), B (powder); B is always above A but both pass through the origin and are straight lines. (a)[1 mark]Describe the relationship between rate of reaction and concentration in Experiment A.
(b)[2 marks]Suggest why at every concentration, Experiment B has a greater rate than Experiment A.
(c)[3 marks]Explain how both concentration and surface area affect the frequency of successful collisions in these experiments.
Question 118
2 marks · Normal
Answer and see the solution →Hydrated cobalt(II) chloride can be heated to produce anhydrous cobalt(II) chloride and water. The process is reversible.
State the chemical equation for this reversible reaction, using the correct symbol, and explain what the symbol means.
Question 119
4 marks · Normal
Answer and see the solution →The reversible reaction between hydrogen and iodine to form hydrogen iodide can reach dynamic equilibrium in a sealed tube.
(a)[2 marks]State what is meant by dynamic equilibrium.
(b)[2 marks]Describe two conditions necessary for dynamic equilibrium to occur in this reaction.
Question 120
3 marks · Normal
Answer and see the solution →At dynamic equilibrium in a sealed vessel, the following reversible reaction occurs:
Suppose the rate of the forward reaction is 0.160 mol dm⁻³ min⁻¹ when equilibrium is reached. Calculate:
(a)[1 mark]The rate of the reverse reaction at equilibrium.
(b)[2 marks]If 0.160 mol of N2O4 is used up in 1 minute, how much NO2 would be produced in that time by the forward reaction?