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Name ________________

Name ________________

Chemistry Period ____

Date _________________ Le Chatelier’s Principle LAB


Le Chatelier’s Principle states that when a system at equilibrium is disturbed by an external stress, the system will react in such a way so as to counteract that stress. Stresses can include changes in temperature, pressure and concentration. The equilibrium system you will observe in lab today, results when copper (II) chloride is dissolved in water.


CNAME CHEMISTRY PERIOD DATE LE u2+(aq) + 4Cl-(aq) + heat CuCl42- (aq)

blue clear green


You will apply an external stress to the system and compare the shift in equilibrium to your predictions.

Materials

copper (II) chloride (CuCl2) dropper plate

two test tubes sodium chloride/salt (NaCl)

two 250 mL beakers 1.5 M copper (II) chloride

AgNO3(aq) 4.0 M NaCl(aq)

10 mL graduated cylinder dropper pipet

Procedure

  1. Rinse out a dropper plate. Set aside for procedure step 9.

  2. Make 20.0 mL of 1.5 M copper (II) chloride solution in a 100 ml grad cylinder. Note the color of this solution. This will be your stock solution.

  3. Make 10.0 mL of 4.0 M sodium chloride solution in 10 ml grad cylinder. Set aside for procedure step 11.

  4. Create a hot water bath by filling a 250 mL beaker half full with hot water from the faucet.

  5. Create a cold water bath by filling a second 250 mL beaker half full with ice and cool tap water.

  6. Place 3.0 mL of copper (II) chloride solution into each of the two test tubes.

  7. Place one test tube in the hot water bath, the other into the cold water bath.

  8. After a few minutes, record the color of the solution in each of the test tubes.

  9. Fill two wells of a dropper plate half full with copper (II) chloride solution.

  10. Add approximately 2.0 mL of sodium chloride solution to one of the wells. Use the other well as a control and record your observations.

  11. Fill two clean wells of the dropper plate half full with copper (II) chloride solution.

  12. Add 3-5 drops of silver nitrate to one of the wells. Use the other well as a control and record your observations.

  13. Clean up you area and wash all glassware the dropper plate. Place any excess copper (II) chloride solution into the designated waste container. Excess sodium chloride solution can be put down the drain.


Prelab Questions

1. What will be the indication that the equilibrium shifted to the right, favoring the forward reaction and therefore the products?


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2. What will be the indication that the equilibrium shifted to the left, favoring the reverse reaction and therefore the reactants?


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3. Complete the following table as a representation of your hypothesis:


External Stress

Prediction of Shift (right/left)

Prediction of Color Change

Heat solution



Cool solution



Increase [chloride ion]



Decrease [chloride ion]




4. Calculate the mass of copper (II) chloride required to make 20.0 mL of 1.5 M CuCl2(aq).







5. Calculate the mass of sodium chloride required to make 10.0 mL of 4.0M NaCl(aq).






Data and Observations

Create your data table(s) using a straight-edge ruler. For your qualitative data table, be sure to leave enough space for neatly written descriptions of your observations.

















Analysis

1. Based on your observations, how does a decrease in temperature affect the [CuCl42-] and [Cu2+]?


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2. Based on your observations, how does an increase in temperature affect the [CuCl42-] and [Cu2+]?


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3. Explain how adding NaCl(aq) affects the concentration of the chloride ion in solution?


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4. Based on your knowledge of solubility rules, explain how adding AgNO3 affects the concentration of the chloride ion in solution? Write an ionic equation to support your answer.


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Ionic equation for AgNO3(aq) + CuCl2(aq)


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