Required practical 7: measuring rate of reaction

Describe the initial rates method

• put each experiment in separate burette

• Measure out required volume of KI, sodium thiosulfate, starch and water into a conical flask from the burette

• Measure hydrogen peroxide in a test tube

• Pour hydrogen peroxide from the test tube into the conical flask and immediately start the timer with swirling

• Colour change (blue-black)

Describe the continuous rates method

• measure 50cm of 1mol dm-3 of HCL and add to conical flask

• Set up gas syringe

• Weigh 0.3gof magnesium and add to conical flask

• Place bung firmly and start timer

• Record volume of gas collected every 15 seconds for 3 minutes

Give an improvement for the initial rates method

• use a colorimeter to reduce human error

Why may the concentration of one reactant have a large excess?

• does not affect rate and will be zero order because the concentration remains constant

How can you determine the order of reaction?

• through repeating the experiment and changing the concentrations