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                     Le Chatelier’s Principle Virtual Lab

 Pre-Lab Questions

 1) Which describes a solution that contains a system at equilibrium? Explain your
        One in which the color of the solution is changing slowly, or one in which the
        color is not changing.

 2) Methanol has the formula CH3OH and can be produced by the reaction of carbon
    monoxide with hydrogen gas.

                                CO + 2 H2       CH3OH + heat

   In an attempt to maximize the yield of methanol (amount of methanol produced), a
   chemist would try to shift the equilibrium as far to the right as possible. Which of the
   following would accomplish this?
           a. heating the mixture
           b. adding an excess of carbon monoxide
           c. removing the methanol as it is formed
           d. adding a substance that reacts with carbon monoxide


 I. Cobalt System:

          CoCl4-2 {blue} + 6 H2O            Co(H2O)6+2 {red} + 4 Cl- + heat

 Note: Adding KCl adds K+ and Cl- ions. Adding AgNO3 adds Ag+ ions that react with
 Cl- ions, removing them from the system.

Action        Observation          Shift                          Explanation


 Add H2O

 Add KCl

Add AgNO3

   II. Ammonium System:

                          heat + NH4+ + OH-        NH3 + H2O

   Note: Adding NH4Cl adds NH4+ and Cl- ions. When added; HCl dissociates to form H+
   ions that react with OH- ions, removing them from the system. Adding NaOH adds Na+
   and OH- ions. More OH- makes it pink, less makes it clear.

 Action         Observation        Shift                      Explanation

Add NH4Cl

 Add HCl

Add NaOH

   III. Iron Thiocyanate System:

                Fe+3 {pale yellow} + SCN-        FeSCN+2 {red} + heat

   Note: Adding KSCN adds K+ and SCN- ions. Adding Fe(NO3)3 adds Fe+3 and NO3- ions.
   Adding Na2HPO4 adds HPO4-2 ions which react with Fe+3 ions, removing them from the

 Action         Observation        Shift                      Explanation


Add Fe(NO3)3

Add Na2HPO4

    IV. Chromate System:

                   2 CrO4-2 {yellow} + 2 H+          Cr2O7-2 {red} + H2O

    Note: HCl dissociates to form H+ and Cl- ions. Adding NaOH supplies OH-
    ions that react with H+ ions, removing them from the system

   Action        Observation         Shift                        Explanation

  Add HCl

 Add NaOH

    V. Nitrogen Dioxide System:

                    2 NO2(g) {brown}          N2O4(g) {colorless} + heat

   Action        Observation         Shift                        Explanation




    Be sure to give explanations, not just one word answers.

    1. What would happen to the ammonium system if it was heated?

    2. What would happen to the nitrogen dioxide system if pressure were increased?
3. What would happen if the pressure were increased on the system below?

       H2(g) + Cl2(g) ↔ 2HCl(g)

4. Hemoglobin (Hb) and oxygen gas form a complex (HbO2) that carries oxygen
throughout the human body. Unfortunately, carbon monoxide also binds to hemoglobin
so that an equilibrium is established. Carbon monoxide poisoning occurs when the
concentration of HbO2 in the blood is reduced.

                               HbO2 + CO        HbCO + O2

  The first aid for a person suffering from carbon monoxide poisoning is to (1) remove
them to an area of fresh air, and (2) administer oxygen. Using the principles of equilibrium,
explain how each of these helps to restore the HbO2 concentration.

4. You are hired at a factory that manufactures methane gas (CH4). What could be done
at this factory to maximize production? You must include at least 5 actions that could be
taken to get full credit.

                   CO(g) + 3H2(g) ↔ CH4(g) + H2O(g) + heat

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