Investigate the effects of various catalysts on the decomposition of hydrogen peroxide.
It is important in this practical to use appropriate apparatus to make and record a range of measurements accurately, including time, mass and volume. This includes the safe use of apparatus, and monitoring chemical changes.
This outlines one way to carry out the practical. Eye protection must be worn.
To investigate the effect of different catalysts on the rate of a reaction.
Hydrogen peroxide solution decomposes slowly at room temperature to water and oxygen:
hydrogen peroxide → oxygen + water
2H2O2(aq) → O2(g) + 2H2O(l)
The volume of oxygen given off can be measured using a gas syringe, or by collecting in an inverted measuring cylinder. The effectiveness of the catalyst can be judged from the initial rate of the oxygen production.
Record the results in a table. This table gives some example results of the volume of gas produced every ten seconds.
|Catalyst||10 s||20 s||30 s||40 s||50 s||60 s|
Which is the best catalyst for the decomposition of hydrogen peroxide? Explain your answer.
Manganese dioxide is the best catalyst because it produces the highest volume of oxygen more quickly. A graph of volume of oxygen against time has the steepest gradient for this catalyst.
Suggest a reason why the same mass of catalyst is used in each experiment.
The surface area to volume ratio of the catalyst may affect the rate. It cannot be precisely controlled, but the same mass of powdered catalyst will have roughly the same surface area to volume ratio.
Evaluate the hazards and the precautions needed to reduce the risk of harm. For example:
|Hydrogen peroxide is corrosive||Hydrogen peroxide could get onto the skin when adding to test tube||Wash hands immediately if any hydrogen peroxide gets onto them|
|Powdered catalysts||Many powdered catalysts can be irritants if inhaled||Avoid spilling the powdered catalysts|