Surface area and rate

demonstration

This activity vividly demonstrates the relationship between surface area and rate of reaction .

 

Safety

Potassium manganate is a strong oxidant.

Apparatus :

- Potassium manganate (KMnO4)
- Glycerol
- mortar and pestle
- 2 evaporating dishes
- 2 X 10 mL measuring cylinders

 

  

Step 1 Place a 1.00 gram sample of potassium manganate in an evaporating dish, as shown above.

 

Step 2 Finely crush a 1.00 gram sample of potassium manganate using a mortar and pestle. Place it into an evaporating dish, as shown above.

Place both evaporating dishes in a fume cupboard

 

Step 3 Measure 2 mL of glycerol in each measuring cylinder and simultaneously pour into the evaporating dish on top of the potassium manganate.

Close the hood of the fume cupboard and wait.

Before ignition white smoke should appear coming from the mixture of glycerol and potassium manganate.

View the video on the right. You will see two crucibles in a fume cupboard. On the right is finely ground potassium manganate. On the left is the potassium manganate with large crystals.
1) Why is the rate of some chemical reactions increased when the surface area of the reactant is increased?
2) Using the collision theory explain why as the mixture heats up the reaction accelerates.

3) From the list below, which are factors that will increase the rate of a chemical reaction? Explain why in terms of collisions.
4) Increasing the surface area of the reactants increases the speed of the reactant molecules
5) Increasing the concentration of the reactants increases the speed of the colliding molecules.
6) Temperature increases the concentration of the reactants and speeds up the rate of reaction.