Chemical Equilibrium Chapter 13

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Chemical EquilibriumChapter 13

• LeChateliers Principle

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The Copper Complex Equilibrium System

• Cu(H2O)4 2 4Cl1- ? CuCl42- 4H2O

Blue
Green
Add NaCl to the system until a change is noted.
What has happened? What is happen to this
reaction if it is heated? Where is the energy?
Which reaction is exothermic?
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LeChateliers Principle Concentration

• If a component (reactant or product) is added to
  a reaction system at equilibrium (at constant T
  and P or constant T and V) the equilibrium
  position will shift in the direction that lowers
  the concentration of that component. If a
  component is removed, the opposite effect occurs.
• DOES NOT CHANGE K.
• As4O6 (s) 6 C(s) ? As4 (g) 6CO(g)

What happens if you Add CO to the system? Add
As4O6 to the system? Remove As4?
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LeChateliers Principle Pressure

• Increasing a the pressure favors the side with
  the fewest particles
• Decreasing the pressure favors the side with the
  most particles
• DOES NOT CHANGE K.
• Three way to change pressure
• Add or remove a gaseous reactant or product.
• Add an inert gas (one not involved in the
  reaction).
• Change the volume of the container.

Predict the shift in equilibrium position that
will occur for each of the following processes
when the volume is reduced. P4 (s) 6Cl2 (g) ?
4PCl3 (l) PCl3 (g) Cl2 (g) ? PCl5 (g) PCl3 (g)
3NH3 (g) ? P(NH2)3 (g) 3HCl (g)
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LeChateliers Principle Temperature

• Increasing the energy favors the endothermic
  reaction.
• Decreasing the energy favors the exothermic
  reaction.
• The value of K changes with temperature.
• N2 (g) 3H2(s) ? NH3 (g) 92kJ What will
  happen to K if temp. is increased?
• 92kJ CaCO3 (s) ? CaO (s) CO2(s) What will
  happen to K if temp. is increased?

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LeChateliers Principle Temperature
Predict how the value of K changes as the
temperature increases. N2 (g) O2 (g) ? 2NO (g)
?H? 181 kJ 2SO2 (g) O2 (g) ? 2SO3
(g) ?H? -198 kJ
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The Copper Complex Equilibrium System

• CoCl42- 6H2O ? Co(H2O)62 4Cl-

Blue
Pink
Add a pea size piece of CoCl26H2O to the beaker
then add 6M HCl to the beaker. What is
favored at this equilibrium? Add water to the
beaker until you notice a change. How
did the equilibrium system shift? What
happened to the concentration of CoCl42-? Heat
the beaker in a hot water bath. How did
the equilibrium system shift? Where is
energy in this system? Which reaction is
the endothermic reaction? What do you think will
happen if the beaker is cooled?
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Problem 57

• Suppose the reaction system below has already
  reached equilibrium. Predict the effect that
  each of the following changes will have on the
  equilibrium position. Tell whether the
  equilibrium will shift to the right or left or
  will not be affected.
• UO2 (s) 4HF (g) ? UF4 (g) 2H2O (g)
• Additional UO2 (s) is added to the system.
• The reaction is performed in a glass reaction
  vessel HF(g) attacks and reacts with glass.
• Water vapor is removed.

1. Right b. left c. right

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Problem 59

• An important reaction in the commercial
  production of hydrogen is below. How will this
  system at equilibrium shift in each of the
  following cases?
• CO (g) H2O (g) ? H2 (g) 2 CO2 (g)
• Gaseous carbon dioxide is removed.
• Water vapor is added.
• The pressure is increased by adding helium gas.
• The temperature is increased (the reaction is
  exothermic).
• The pressure is increased by decreasing the
  volume of the container.

a. Right b. right c. no shift d. left
e. left
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Problem 63

• Old fashioned smelling salts consist of
  ammonium carbonate. The reaction for the
  decomposition of ammonium carbonate is
  exothermic. Would the smell of ammonia increase
  or decrease as the temperature is increased?
• (NH4)2CO3 (s) ? 2NH3 (g) CO2 (g)
  H2O (g)

If the salts were in equilibrium then increasing
the temperature would favor the reverse reaction.
This would produce less NH3 and more salts.
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Problem 64

• Ammonia is produced by the Haber process, in
  which nitrogen and hydrogen are reacted directly
  using an iron mesh impregnated with oxides as a
  catalyst. For the reaction below the equilibrium
  constants (Kp values) as a function of
  temperature are
• Is the reaction exothermic or endothermic?
• N2 (g) 3H2 (g) ? 2NH3 (g)

300?C 4.34 x 10-3
500?C 1.45 x 10-5
600?C 2.25 x 10-6
exothermic