PAG 09 – Rates of Reaction – Continuous Monitoring: Module 1: Practical Skills in Chemistry: Chemistry OCR A A Level

What is the role of manganese dioxide in the decomposition of hydrogen peroxide?

Catalyst

What is the purpose of catalysts?

1. Provide an alternative reaction route with a lower activation energy.

2. Increase the rate of reaction.

What is meant by term ‘half-life’ for a reaction?

The time taken for the reactant concentration to half.

Briefly describe how to find the half-life of the decomposition of hydrogen peroxide.

1. Set up the apparatus to collect any gas produced during the reaction.

2. Record the volume of O2 collected at regular intervals and calculate [H2O2].

3. Plot a graph of [H2O2] against time and use it to find 2 values for the half-life.

Why is it important to rapidly put the bung in the conical flask after H2O2 and the catalyst have been combined?

The reaction will have started so O2 will be produced. If the bung is not in place, oxygen will be escape (this won’t be included in the volume measurement).

Why might the volume of gas be measured in a burette rather than a measuring cylinder?

To obtain more precise measurements.