Standard level
The decomposition of hydrogen peroxide in the presence of a catalyst releases oxygen gas that can be collected in a gas syringe.
Background
The order of reaction is the power to which the concentration of a reactant is raised in the rate equation. Note that solids and/or pure liquids cannot appear in the rate equation as they cannot be expressed as concentrations.
For the decomposition of hydrogen peroxide there is only one reactant that can be said to have a concentration, the hydrogen peroxide itself.
The decomposition of hydrogen peroxide
2H2O2(aq) → 2H2O(g) + O2(g)
The rate equation for this reaction takes the form:
Rate = k[H2O2]x
Where 'x' is the order of reaction with respect to hydrogen peroxide and k is the rate constant.
The rate equation can ONLY be solved by experiment.
Chemicals
- Hydrogen peroxide, 10vol
- Manganese(IV) oxide
Apparatus
- Volumetric flask, 50ml
- Pipette, 25ml
- Gas syringe and delivery tube
- Side-arm tube
- Small metal cap
- Electronic balance
- Thermometer
- Pipette 10cm3 of the hydrogen peroxide solution into the side arm tube
- Weigh out 0.2g of manganese(IV) oxide catalyst in a small metal cap
- Using the tweezers, lower the small metal cap with catalyst onto the surface of the hydrogen peroxide solution.
- Place the bung into the side-arm tube and ensure that the connection to the gas syringe is air-tight.
- Start the timer and carefully shake the side-arm tube to mix the catalyst with the hydrogen peroxide.
- Record the volume of oxygen produced every 10 seconds.
- The residues from the reaction must be kept in a residues container.
- Hydrogen peroxide is an oxidising agent