Sulphuric acid and Sodium Thiosulphate.

Research Question: Evaluating the effect of change in concentration on the Rate of reaction between Sulphuric acid and Sodium Thiosulphate.

General Background: Rate of reaction according to Chemistry third edition IBID indicates how fast reactants are being converted to products during a chemical reaction. It is the rate of consumption of a reactant, or the rate of formation of the product divided by the corresponding coefficient in the stoichiometric equation. The rate has units of mol dm-3 s-1.

Hypothesis: As we will increase the concentration of Sulphuric acid with temperature, catalyst and surface area controlled, the rate of reaction will increase. As the rate at which the particles collide is increased, as there are more particles in closer proximity when higher concentrations are present.

Variables:

Independent: The time taken between the changes of concentrations of Sulphuric acid.

Dependent: The time taken for the reaction to take place until the marked cross disappears due to the cloudy being formed.

Controlled: Temperature, Catalyst and Surface area.

Materials and Apparatus:

Two 10cm3 measuring cylinders

Five 150cm3 beakers

A piece of paper

Felt pen

Two 10cm3 pipettes

Beaker

Stopwatch

Five test tubes

Chemicals:

250 cm3 of 1M Sodium Thiosulphate solution

250 cm3 of 1M Sulphuric acid

Distilled water

Method:

1. Ensure that the temperature is kept constant by performing the experiment under standard conditions (298 K and 1 atm). Temperature is controlled in this experiment as increasing the temperature increases the rate of a reaction because as the temperature increases, the kinetic energy of the particles increases and thus more particles have sufficient energy to react leading to more collisions. Also ensure that no catalyst is used as a catalyst increases the rate of chemical reaction as it lowers down the activation energy of a reaction and the surface area of the beaker does not change as collisions occur on surface thus the larger the particle size the smaller the surface area and the fewer collisions can occur.

2. Make a cross on the paper using the felt tip pen and place it beneath the empty beaker.

3. Form 0.2M of Sulphuric acid by adding 0.2 ml of 1M Sulphuric acid and 0.8 ml of distilled water into a test tube using the measuring cylinder and pipette and label it 1. Form 0.4M of Sulphuric acid by adding 0.4ml of 1M Sulphuric acid and 0.6ml of distilled water into a test tube using the measuring cylinder and pipette and label it 2. Form 0.6M of Sulphuric acid by adding 0.6 ml of 1M Sulphuric acid and 0.4 ml of distilled water into a test tube using the measuring cylinder and pipette and label it 3. Form 0.8M of Sulphuric acid by adding 0.8 ml of 1M Sulphuric acid and 0.2 ml of distilled water into a test tube using the measuring cylinder and pipette and label it 4. Add 10 ml of 1M Sulphuric acid to the fifth test tube and name it 5.

4. Using a different measuring cylinder measure 10 ml of the Sodium Thiosulphate solution with a pipette.

5. Add the mixtures in test tube 1 and the test tube containing Sodium Thiosulphate solution simultaneously into the empty beaker.

6. Start the stopwatch immediately.

7. Stop the stopwatch as soon as the reaction finishes as the cross disappears because of the cloudy mixture formed.

8. Record the time taken for the reaction to occur.

9. Repeat the experiment thrice and take the average of the readings.

10. Repeat the same procedure with test tube 2, 3, 4 and 5.

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