Le Chatelier's Principle

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Lab # 25
2/15/12
Le Chatelier’s Principle Lab

Purpose: To discover the effects of Le Chaterlier’s principle. Description: Chemical reactions can take place both forwards and backwards. When a reaction reacts to form products, some of the products react to form the reactants. In a chemical reaction, when the rate of a forward reaction equals the rate of a backward reaction, it is at equilibrium, where the products and reactants stay constant. If there is a change in condition on either reactants or products, the position of the equilibrium will shift either right or left to try to lessen that change. For example if the pressure of a product is increased, the position of the equilibrium would shift towards the reactant or to the left in order to reduce the pressure of the product. The Le Chatelier’s Principle is a theory that explains what happens when we disturb a reaction after it is already completed. In this experiment, solutions will be prepared, reacted, and then “disrupted” by adding compounds to the mix. Procedure:

Part 1: Obtain 5 ml of saturated NaCl solution in each of two test tubes. Add 10 drops of concentrated 11.7 M hydrochloric acid to one test tube. Same for the other test tube using 1 M instead. Observe for 2 minutes. Part 2: Mix 2 ml of .01 M FeCl3 and 2 ml of .1 M KSCN solutions in a test tube. Dilute this by pouring it into a beaker and adding 100 ml of deionized water. Pour 5 ml of this solution into each of four test tubes, using test tube one as a control, to compare to the others. Follow the below procedure. TT #2: Add 1 ml of .1 M FeCl3 solution.

TT #3: Add 1 ml of .1 M KSCN solution.
TT #4: Add .1 M AgNO3 solution by drops until a change occurs

Part 3: Prepare a dilute ammonia solution (NH3 + H2O NH4+ + OH-) by adding 4 drops of ammonia to 100 ml of water. Add 3 drops of phenolphthalein (detects OH-). Pour 5 ml of the solution into each of three test tubes and follow the below procedure. TT#1: Add several small crystals...
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