The rate of a reaction can be measured by carrying out investigations. During a chemical reaction, it is possible to measure how much reactant is used up or how much product is formed in a certain time.
A chemical change can be measured in three ways: 1. Monitor the production of gas. This can be done in two ways:
a. By collecting the gas in a gas syringe or graduated cylinder.
b. By allowing the gas to escape from the flask and recording the loss of mass.
Gas
Conical flask
Gas syringe
Reaction mixture
Gas
Reaction mixture
z Fig. 12.3.3
Using a gas syringe to monitor volume of gas production in a chemical reaction
2. Monitor the temperature changes during a reaction.
3. Monitor the appearance of the reactants and the products during the reaction. In some cases, the products of a reaction are insoluble. As the product is insoluble, it will become visible and be deposited at the bottom of the flask. In these kinds of reactions, you can measure the time taken for the reaction mixture to go cloudy.
Rate of Reaction Graphs
The slope of a graph can be used to show the rate of change in a reaction.
A fast reaction will produce lots of the product quickly. This will give a steeper slope on the curve when plotted on a line graph, as shown in Fig. 12.3.5.
As the reactants are used up, no more product is formed. This can be seen on a graph when the line levels off.
z
Slower reaction
Reaction finished as the reactants get used up
Volume of product
Reaction slowing
Electronic balance
z Fig. 12.3.4
Recording loss of mass to monitor gas production in a chemical reaction
Cotton wool
Conical flask
12.3
Fast
reaction
The steeper the graph, the quicker the reaction takes place
