This reaction is used in a small oxygen generator for emergency equipment. Fig. 1 shows a sealed reaction vessel containing hydrogen peroxide solution and a...
Question 1 Report
This reaction is used in a small oxygen generator for emergency equipment. Fig. 1 shows a sealed reaction vessel containing hydrogen peroxide solution and a catalyst cartridge. When a valve is opened, the catalyst enters the solution and oxygen is collected in a flexible gas bag. The vessel has a pressure sensor that stops the reaction if gas is made too quickly. Engineers compare catalyst powders with different particle sizes, using the same mass of catalyst each time.
(a) Complete the word equation: hydrogen peroxide → water + ________. [1]
(b) State the role of the catalyst cartridge. [1]
(c) Explain, using collision theory, why a powdered catalyst can give a faster rate than the same mass of pellets. [3]
(d) Give three reasons why the engineers should not simply use the fastest catalyst powder in the generator. [3]
(e) Describe how the gas bag volume could be used to compare the initial rates of two catalyst powders. [3]
(f) Which sensor reading would indicate that the reaction should be slowed: increasing pressure or decreasing pressure? [1]
Answer Details
(a) Hydrogen peroxide decomposes to form water and oxygen. [1]
(b) The cartridge acts as a catalyst: it increases reaction rate without being used up. [1]
(c) Powdered catalyst has a larger surface area than the same mass of pellets. [1] This exposes more catalyst sites to hydrogen peroxide particles. [1] More successful collisions occur each second, so decomposition is faster. [1] [3]
(d) The fastest powder may make the reaction dangerously rapid [1], causing pressure to rise too quickly. [1] It may also cause excessive temperature increase, release oxygen before it is needed, or be difficult to contain. [1] The rate must be controlled for a steady, safe oxygen supply. [3]
(e) Use equal volumes and concentrations of hydrogen peroxide at the same temperature. [1] Use the same mass of each catalyst. [1] Compare gas-bag volumes after the same short time, or compare the initial gradients of volume-time graphs. [1] [3]
(f) Increasing pressure indicates that the reaction should be slowed. [1]
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