Introduction

In most instances when we double the concentration of a reactant the rate of the reaction also doubles. If we plot a graph of concentration vs rate, we would expect a straight line with a positive gradient and can say that the rate is directly proportional to the concentration.

In real life this is not always the case. Sometimes if we double the concentration the rate increases by a factor of four. In this section consider the graphs drawn from experimental data and work out the order of the reaction. From this we can calculate the rate constant.

Reading

Edexcel AS/A Level Chemistry Student Book 2 pages 7 to 14

Tasks

Complete the following:

WATCH - Kinetics: Chemistry’s Demolition Derby (YouTube)

Read pages 7 to 14 and take notes. Take care to carefully review worked examples.
Complete the ‘checkpoint’ questions.
Note subject vocabulary (revision cards are useful).
Draw examples of reaction graphs onto revision cards.

WATCH - The Rate Law: Bozeman Science (YouTube)

WATCH - The Rate Constant: Bozeman Science (YouTube)

Practical Knowledge

WATCH - Reaction of Calcium Carbonate with Hydrochloric Acid (YouTube)

REVIEW & COMPLETE - Practical Exercise 4.1: The Kinetics of the Reaction between Calcium Carbonate and Hydrochloric Acid

For further information review the following student sheet and video:

REVIEW - Practical Exercise 4.1 Further Information (Nuffield Information)

WATCH - Calcium Carbonate Rate of Reaction (YouTube)

When you have completed the virtual practical, check your answers:

CHECK - Practical 4.1 Answers

WATCH - Reaction Between Iodine and Propanone in Acid Solution (YouTube)

REVIEW & COMPLETE - Practical Exercise 4.2: The Kinetics of the Reaction between Iodine and Propanone in Acid Solution

When you have completed the virtual practical, check your answers:

CHECK - Practical 4.2 Answers

REVIEW - Kc Calculation (PowerPoint)

Top Tips

Make sure that you understand the following key points:

UNITS! Work them out with care.
All reactant species before the rate determining step will have an effect on the rate of the reaction and will appear in the rate equation.

Key Terms

Add the following key terms with definitions to your glossary.

Rate equation
Order
Overall order
Rate determining step
Half life
Instantaneous reaction rate