I don't remember this very well, but I'm pretty sure Mr Mitchard gave me an E for it.

1. HL Chemistry AssiaChelaghma
Using Colorimeter to Determine the Effect of
Concentration on the Rate of Reaction
Introduction:
When a light passes through a solution in a tube, electrons absorb light. The intensity of the
light emitted through the tube will be less than the light absorbed.
Copper II powder reacts with hydrochloric acid according to the equation:
Cu(s) + 2HCl(aq) → CuCl2(s) + H2(g)
When the reaction takes place, copper II chloride and hydrogen gas are produced. The
concentration of hydrochloric acid decreases. Colorimeter is used to determine the rate of
reaction by measuring the absorbance of a monochromatic light by the solution that contains
excess copper II and hydrochloric acid. When the absorbance of light is obtained, the rate of
reaction can be determined.
Researchquestion:
How do different concentrations of 5cm3 hydrochloric acid that react with 20g of copper II
powder affect the rate of reaction?
Variables:
Independent variables:
The concentration of hydrochloric acid.
Dependant variables:
The absorbance of light during three minutes.
Controlled variables:
 Temperature of the solution must be kept constant so I will use a thermometer of
check the temperature of the solution and keep it constant.
 Volume of the solution must be kept constant. So I will use the same volume of
hydrochloric acid and the same mass of copper II.
 Time should be the same so that I can compare the absorbance of light between
different concentrations.
 Intensity of the monochromatic light should be kept the same.
Apparatus:
 Electronic balance to 0.01g.
 Five test tubes for different solutions of hydrochloric acid (of different
concentrations).

2. HL Chemistry AssiaChelaghma
 Colorimeter to measure the absorbance of light.
 Two temperature sensors
 Five containers, each one contains 20g of Copper II powder
 Five different solutions of hydrochloric acid of these different concentrations:
0.25𝑚𝑜𝑙 𝑑𝑚−3
; 0.50𝑚𝑜𝑙 𝑑𝑚−3
; 0.75𝑚𝑜𝑙 𝑑𝑚−3
; 1.25𝑚𝑜𝑙 𝑑𝑚−3
; 1.50𝑚𝑜𝑙 𝑑𝑚3
Designof the experiment:
The picture below shows how the colorimeter works:
The picture below shows a real colorimeter:
Method:
 Set up the experiment shown in the design above.
 Put 20g of copper II powder in the tube of the colorimeter.
 Set the colorimeter on with the monochromatic light.
 Put one temperature sensor inside the tube that contains copper II to control
temperature of the solution later.
 Put the other temperature sensor in the room to keep room temperature under control.
 Add 5cm3 of hydrochloric acid to the copper II.
 Take the results of the absorbance of light.
 Propagate the graphs and calculate the order of reaction.
 Repeat the experiment using another concentration and then find the order of reaction.

3. HL Chemistry AssiaChelaghma
 Compare the results and find out how does the concentration affects the order of
reaction.
Developing a method for collection of data:
I will repeat the experiment three time for five different concentrations so that I can get
enough data that can be used to find out the effect of concentration on the rate of reaction.
Sources:
https://www.colonialscientific.com/OScatalog/index.php?cPath=152_194
http://www.docbrown.info/page07/appendixtrans09.htm