Unit 10.6.3: Measuring the initial rate of reaction using gas evolution
The students have seen the measurement of average rate in the acid-thiosulfate experiment (10.5.2) and should know that the rate depends on the concentration of the reactants. It follows then that the rate changes as the reactants are used up.
The only time that the actual concentration of reactants is known is at time = 0s.
Hence determination of the initial rate is a useful tool.
This can be carried out by measuring the gradient of the tangent to the volume-concentration curve at time = 0.
To use the reaction between sulfuric acid and magnesium ribbon to collect the hydrogen gas and produce a graph of volume against time with which to determine the initial rate of reaction.
The reaction is exothermic and this could be an entry into discussions about errors and inaccuracies.
This technique will be used in the following experiment.