The apparatus needed depends on the equipment available.
The rate can be measured by placing the reaction container on top of a black ‘X’ before adding the chemicals together (example shown in diagram below). If you time how long it takes until you can no longer see the X due to the formation of the precipitate, you can calculate the rate using the equation.
rate = 1 ÷ (time taken for X to be obscured)
The amount of light passing through the reaction can be measured directly using a light sensor and a data logger. The rate can then be calculated by using the light sensor to work out how long it takes for the light level to stop decreasing.
Advantages for inspection/disadvantages for light sensor:
Advantages for light sensor/disadvantages for inspection: