Le Chatelier's Principle

Le Chatelier's Principle

Introduction:

Le Chatelier's Principle states that if a change is made to a system

in equilibrium, the system reacts in such a way as to tend to oppose

the change, and a new equilibrium is formed. For example, whatever is

done to the equilibrium, the system does the opposite. If something is

added to a system at equilibrium, the system will behave as to remove

it and vice versa. By increasing the concentration of a reaction, it

will result in an increase of the rate of reaction. The new

equilibrium will have a higher concentration of products too. The

system has shifted to relieve the stress. Therefore, the forward and

backward reactions have a balanced equilibrium system. For example: A

+ B [IMAGE] C + D

If the concentration of the reactants B is increased, the equilibrium

will shift to the right, therefore forming more products. If

concentration of C increases, equilibrium will shift to the left

forming more A and B.

Aim:

To investigate Le Chatelier's Principle and effect of concentration

changes on the position of equilibrium

Requirements:

Potassium thiocyanate, KCNS (0.5g)

Iron (III) chloride FeCL3, (0.5g)

Ammonium chloride NH4CL, (0.2g)

Potassium iodine KI, (0.2g)

Sodium hydroxide NaOH, 2M, (1mL0

Acidified hydrogen peroxide H2O2, 20 volume (1mL)

Concentrated hydrochloric acid HCL, (0.5mL)

Ammonia NH3, 2M, (1mL)

Ammonium chloride NH4CL, (2g)

Phenolphthalein (1mL)

Test tubes and rack

White tile

Spatula

Teat pipette

Procedures:

1. 3mL of water was added to 2r.g. of KCNS in the test tube and it

was swirled to dissolve the KCNS. 2r.g. of iron (III) chloride was

added. Observations were recorded.

2. 4 drops of the solution was placed on the white tile and 1 r.g.

of iron ( ) chloride was added to the first, 1r.g. of ammonium

chloride was added to the second, 1 r.