Chemical Equilibrium, chemistry assignment help

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Explanation & Answer

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Abstract
The aim of this experiment is to study how the equilibrium system is affected by changes in
concentration and temperature. The direction of shift for a particular equilibrium system was
known through observation of the system`s color after the temperature of the system has been
changed. The system of this experiment was carried out at three different temperatures in
sealed tubes. Despite the fact that it was hard to measure the concentration of various
solutions, the results were quite good.
Introduction
This experiment pertains qualitative description of certain equilibrium systems before and after
placing the stress on the system. Le Chatelier`s principle is used in describing the observations.
This is done after knowing if the reaction is exothermic or endothermic. The equilibrium shifts
to evolve the heat when the stress such as an increase in temperature is applied and this results
to an exothermic reaction since it entails evolving of energy. The reverse of exothermic is
endothermic e.g. a decrease in temperature causes a reverse effect on the position of the
equilibrium. This experiment is important since it is involved in many biological and chemical
processes. For example, Ph balance of the blood and production of various industrial compounds
are based on equilibrium systems.
Procedure
I.

Effect of change in concentration on Equilibria

Procedure A. Cu2+, NH3, Cu(NH3)42+ Equilibrium System:
Cu2+(aq) + 4NH3 (aq)
Light blue



Cu(NH3)42+
Deep Blue

1. Add about 1 mL of 0.1M CuCl2 solution to each of two test tubes.
2. Add 15M NH3 solution dropwise to each of the two test tubes until the color becomes
more intense. The color change is due to the formation of the complex ion, Cu(NH3)42+.
3. To test Tube 2, add dropwise 4M HNO3 until the color intensity changes. Compare the
color change to that in test tube 1. Account for any color change in terms of a shift in
equilibrium.
4. Add several drops of 15M NH3 solution to test tube 2 to reverse the equilibrium.

5. Compare the color of the solution to the color of the solution in test tube 1.
6. Account for the results
Dispose the solutions as per instructions and continue with procedure B
Procedure B. Phenolphthalein Equilibrium System
The equilibrium may be represented by:
HIn ⇌ H+ + In-

Acid form

base form

(colorless)

(Red)

1. To each of three clean tubes add 2-3 drops of phenolphthalein and about 1 mL of distilled
water. Mix thoroughly.
2. Add 5 drops of 0.1M HCl to test tube 2. Mix and compare the color to that in test tube 1.
Account for the results.
3. Add 5 drops of 0.1M NaOH to test tube 3. Mix and compare the color to that in test tube
1. Account for the color change. Clean the test tubes and proceed to procedure C.

Procedure C. Co2+, Cl-, CoCl42- Equilibrium system

1. To each of four test tubes add 10 drops of 0.1M CoCl2 solution. Now add 10 drops of
concentrated HCl to each test tube with caution. The equilibrium is represented by the
equation:
Co (H2O)62+ + 4Cl- ⇌ Co Cl42- + 6H2O

2. Use Test tube 1 for comparing color change. Save test tubes 1,2 and 3 for procedure IIB
(Temperature Effect on Equilibria).
3. To test tube 4, add drops of distilled water and compare the color to that in Test tube 1.
Record and explain the change. Dispose waste in proper waste container.
4. Clean Test Tube 4 and proceed to Procedure D.
Procedure D. Fe3+, SCN-, Fe(SCN)2+ Equilibrium system

1. In a clean 250-mL beaker add 50...


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