AQA GCSE Chemistry (8462), Higher tier · The rate and extent of chemical change › Rate of reaction
Practise Catalysts. 14 exam-style questions on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.
Cover the answers and test yourself. The app has these as flashcards that come back just before you'd forget them.
What is a catalyst?
A substance that increases the rate of a reaction without being used up.
What name is given to the catalysts found in living things (biological systems)?
Enzymes
How does the equation show that catalase is acting as a catalyst?
Catalase does not appear in the equation.
Complete the sentence. A catalyst changes the rate of a chemical reaction, but is not changed ________ or used up by the reaction.
chemically
Sample questions
Written for this site in the style of AQA exam questions. They are not taken from real past papers.
Question 1Easy4 marks
(a) What is a catalyst?[2]
(b) What name is given to the catalysts in living things?[1]
(c) How does a catalyst increase the rate of a reaction? Tick (✓) one box.[1]
It gives the particles more energy.
It provides a different reaction pathway with a lower activation energy.
It increases the temperature of the mixture.
It increases the concentration of the reactants.
Show the answer and mark scheme
(a)Answer: A substance that increases the rate of a reaction without being used up.
a substance that increases / changes the rate of a reaction
without being used up (in the reaction)
(b)Answer: Enzymes
enzymes
(c)Answer: It provides a different reaction pathway with a lower activation energy.
Question 2Medium3 marks
A student compared two catalysts for the decomposition of hydrogen peroxide solution. The student used the same volume and concentration of hydrogen peroxide solution and the same mass of powdered catalyst each time, and collected the oxygen produced in a gas syringe for 60 s.
With manganese(IV) oxide: 48 cm3 of oxygen collected in 60 s.
With copper(II) oxide: 4.0 cm3 of oxygen collected in 60 s.
(a) Calculate the mean rate of reaction with each catalyst. Give your answers in cm3/s.[2]
(b) Calculate how many times faster the reaction was with manganese(IV) oxide than with copper(II) oxide.[1]
A company makes a chemical by reacting two gases. Without a catalyst, the reaction needs a temperature of 450 °C to go at a useful rate. With a solid catalyst, the reaction goes at the same rate at 250 °C.
(a) Explain why the catalyst allows the reaction to go at the same rate at a lower temperature.[2]
(b) Give two advantages of using a lower temperature.[2]
(c) The catalyst is used as a fine mesh or as small pellets, not as large lumps. Explain why.[2]
(d) The catalyst is not used up, but it still needs to be replaced after several years. Suggest one reason why.[1]
Show the answer and mark scheme
(a)Answer: The catalyst lowers the activation energy, so at 250 °C enough particles still have at least the activation energy.
the catalyst provides a pathway with a lower activation energy
so at 250 °C enough particles still have energy greater than or equal to the (lower) activation energy / there are the same number of successful collisions per second
(b)Answer: Less energy is needed, so costs are lower; less fossil fuel is burned, so less carbon dioxide is released.
less energy / fuel is needed, so energy costs are lower
less fossil fuel is burned, so less carbon dioxide is released
it is safer / there is less risk of burns or fire
the equipment does not have to withstand such high temperatures, so it is cheaper to build and maintain
(c)Answer: This gives a larger surface area, so more reactant particles can collide with the catalyst surface at the same time.
this gives a larger surface area
so more reactant particles can collide with / react on the catalyst surface at the same time
(d)Answer: Impurities in the gases coat the surface of the catalyst.
impurities coat / react with the catalyst surface (poisoning it) / the surface becomes damaged or blocked / some catalyst is lost over time