Le Chatlier's Principle

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Le Chatelier’s Principle
Samuel Song- Parter: Tom Sizeland
Dr. Hauptfleisch: CHE-102L-01
Performed: 3/25/13 Due: 4/12/13

Le Chatelier’s Principle states that “if a chemical system at equilibrium experiences a change in concentration, temperature, volume, or partial pressure, then the equilibrium shifts to counteract the imposed change and a new equilibrium is established (Atkins,1993).” In equilibrium the chemical reactions are a two way reactions and if there are changes in various factors, the equilibrium will be pushed to change to form a new equilibrium.

The purpose of this experiment was to portray this very principle and how these pushes in equilibrium of changing the concentration of specific ions or changing the temperature (energy level) will cause the equilibrium to be shifted. It was hypothesized that observable changes in equilibria would be noticeable and observed with these specific pushes if this principle holds true. Materials:

The materials used and needed to perform this experiment included an electric hot plate, ice cubes, polyethylene transfer pipets, test tubes, 100 mL beaker, de-ionized water (H2O) and the chemicals : 1 M K2CrO4, 3 M H2SO4, 6 M NaOH, 0.1% methyl orange indicator, 0.1% phenolphthalein indicator, 6 M HCl, 0.1 M CH3COOH (acetic acid), 1 M NaCH3COO (sodium acetate), 0.1 M NH3, 1 M NH4Cl, 0.1 M Fe(NO3)3, 0.1 M KSCN (potassium thiocyanate), 0.15 M anhydrous CoCl2 (in methanol), 12 M HCl, 5.4 M NaCl, 0.1 M BaCl2, 0.1 M CaCl2, 0.5 M H2C2O4 (oxalic acid), 0.5 M K2C2O4 (potassium oxalate), 6 M NH3. Concentrated chemicals such as 12 M HCl, or even 6 M HCl, are very corrosive. Goggles and gloves must be worn at all times. The mixtures of chemicals must also be accordingly disposed. Also the heating of methanol causes toxic and flammable vapors, thus requiring this procedure to be performed under a hood.

The first manipulation of equilibrium required 1 M K2CrO4, 3 M H2SO4, and 6 M NaOH. 3 mL of 1 M K2CrO4 was added to a test tube then several drops of 3 M H2SO4 were added. The test tube was swirled to mix the two chemicals and any observed change was recorded. Then several drops of 6 M NaOH were added to the same test tube and the mixture was stirred until a change occurred. This change was then recorded. Several drops of 3 M H2SO4 was again added to the mixture and stirred. This change was also recorded.

In the second equilibrium manipulation, a drop of methyl orange indicator was added to 3 mL of water in a test tube. Two drops of 6 M HCl was then added and any changes were recorded. Following the two drops of HCl, 4 drops of 6 M NaOH was added to the mixture and changes in color were recorded. After this procedure, the experiment of these chemicals was repeated, but the phenolphthalein indicator was used in place of the methyl orange indicator.

In the third equilibrium manipulation, two test tubes were prepared with 3 mL samples of 0.1 M acetic acid and a drop of methyl orange indicator. To one of the samples 1 M sodium acetate was added by a few drops at a time. With mixing, the changes in color of both tests tubes were compared and recorded.

In the fourth equilibrium manipulation, two 3 mL samples of 0.1 M NH3 was prepared with a drop of phenolphthalein indicator. The initial color of these samples were noted and recorded. Then to one sample, 1 M NH4Cl was added and mixed a few drops at a time. To the other sample, 6 M HCl was added one drop at a time with mixing. With both samples any change in color and odor was recored.

In the fifth equilibrium manipulation, 3 mL of 0.1 M Fe(NO3)3 was added to 3 mL of 0.1 M KSCN in a 100 mL beaker. Changes in color were recorded. This mixture was then diluted by adding 50 to 60 mL of water until the deep red color was reduced in intensity. Then 5 mL of this solution was placed in a test tube and 25 drops of 0.1 M Fe(NO3)3 was added. Any changes in color were recorded. To a second sample of 5 mL of the...
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