Equilibrium Experiment

Topics: Sodium chloride, Sodium, Chemical equilibrium Pages: 4 (901 words) Published: June 19, 2013
Experiment 5: Shifting Equilibrium

A solution is in equilibrium when the rate of forward reaction and the rate of reverse reaction are equal. This equilibrium may be disturbed when the concentration of the reactants, the concentration of the products or the temperature is changed. If the process involves gases, a change in pressure can also affect the position of equilibrium. The concept behind this is Le Chatelier's Principle which states that when a system is disturbed through application of a particular stress, the system shifts to the direction which relieves the stress. The shifting equilibrium experiment will further explain this concept and discuss the reaction quotient and equilibrium constant.

Seven test tubes were filled with 2.0 mL of 0.10 M Cu(NO3)2 and into each test tube, 1.0 mL of 0.10 M NaOH was added. Using a centrifuge, the precipitate was settled and the supernate was discarded. 3.0 mL of distilled water and 10 drops of 0.10 M NaOH were added into each test tube. The test tubes were then prepared according to Table 1.

Table 1. The reagents to be added for Cu(OH)2(s) equilibrium Test tube| Reagent to be added|
1| 2.0 mL distilled water|
2| 2.0 mL 1.0 M H2C2O4 solution|
3| 2.0 mL water + pinch of Zn dust|
4| 2.0 mL of 1.0 HNO3|
5| 2.0 mL of 6.0 M NH3|
6| 2.0 mL of 0.10 M Na3PO4|
7| 2.0 mL of 0.10 M Cu(NO3)2|

Each mixture was shaken thoroughly. The observations, specifically, the change in colour or amount of precipitate for each test tube are shown in Table 2.

Table 2. Changes in the precipitate in each test tube
Test tube| Observations|
1| no colour change, less precipitate|
2| turned light blue, less precipitate|
3| turned grey, |
4| no precipitate |
5| turned dark blue, less precipitate|
6| more precipitate|
7| turned light blue|

The Keq expressions for the reactions in test tubes 1-5 were determined. There was no test tube where...

References: Goldberg, D. (2007). Fundamentals of chemistry. (5th ed.). McGraw-Hill Companies Inc.
Silberberg, M. (2009). Chemistry the molecular nature of matter and change. (5th ed.). New York: McGraw-Hill Companies Inc.
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