Rate and Extent of Reaction

The following topics are covered next:

• What the term reaction rate means

• The factors affecting reaction rates

• How to measure rates of reaction

• The mechanisms of reaction and the effect of catalysts

There are several experiments in this tutorial. The learners will be using dangerous chemicals and should be properly instructed on the correct use of safety equipment, including safety goggles, gloves and protective clothing. They should also be reminded not to sniff any chemicals as the fumes can be dangerous as well. More information on laboratory procedures as well as safety precautions is provided in Chapter 1 (Science skills).

In the informal assessment the learners must determine a quantitative reaction rate in the reaction of \(\text{Na}_{2}\text{S}_{2}\text{O}_{3}\) and \(\text{HCl}\). Learners are required to perform the experiment, calculate quantitative reaction rates (using the formation of precipitate), and plot a graph of their results.

Introduction

A car slowly rusting away, a match burning, a tablet dissolving in water. All of these are chemical reactions and all of these take place at different rates. If you were to hold a race between these three reactions you would find that the match wins (it burns quickly), while the car rusting would lose (it may take years to rust).

A rusting car, a match burning and a tablet dissolving in water.

In the next set of lessons, we will look at why reactions proceed at different rates (speeds) and how we can change the rate of the reaction.