Practical Eighteen-Le Chatelier's Principle

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Kelly, Gavin & Siew Peng

Practical Eighteen-Le Chatelier’s Principle

Date: 25.10.04

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  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.

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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 ...

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