 At 25oC, K = 0.90 for the reaction
H2O(g) + Cl2O(g) ↔ 2HOCl(g)
Calculate the concentrations of all species at equilibrium when you
start with 1.0 g of H2O and 2.0 g of Cl2O mixed in a 1.0 L flask.
2 HBr(g) ↔ H2(g) + Br2(g)
 a) A 55.4 g sample of HBr is placed in an evacuated 6.00 L container
at 1500C.
What is the concentration in mole per liter of HBr before any
decomposition occurs?
b) If the HBr is 43.5 percent decomposed when equilibrium is
established at 1500C, calculate the value for the equilibrium
constant, Kc, for this decomposition reaction.
c) In order to produce some HBr, a 1.50 mole sample of H2 is first
placed in an empty 2.00 liter container maintained at a temperature
different form 1500C. At this temperature, Kc equals 0.125. How
many moles of Br2 must be added to the container to reduce the
moles of H2 to 0.800 mole at equilibrium.
Le Chatelier’s Principle
You have heard of Newton’s law of motion that says for every action there
is an equal and opposite reaction. Well, Le Chatelier’s Principle is some
what similar. It basically says that when a reaction at equilibrium is
disturbed the reaction will undo what was done to it. This is done by
shifting the reaction in a direction that will undo what was done to it.
 In which direction will the position of the equilibrium
H2(g) + I2(g) ↔ 2HI(g)
be shifted for each of the following changes?
a)
b)
c)
d)
e)
f)
H2(g) is added.
I2(g) is removed.
HI(g) is removed.
Some Ar(g) is added.
The volume of the container is doubled.
The temperature is increased. (For HI, ∆Hf = 25.9 kJ/mol)
 What will happen to the number of moles of SO3 in equilibrium with SO2
and O2 in the reaction
2 SO3(g) ↔ 2 SO2(g) + O2(g)
∆H = 197 kJ
in each of the following cases?
a) Oxygen gas is added.
b) The pressure is increased by decreasing the volume.
c) The pressure is increased by adding argon gas.
d) The temperature is decreased.
e) A catalyst is added.
f) Gaseous sulfur dioxide is removed.
 A test reaction is performed in a 4.0 L container holding 55.00 grams of
solid calcium carbonate and some solid calcium carbonate along with
21.40 g of carbon dioxide gas. The reaction that occurs is
CaCO3(s)  CaO(s) + CO2(g) where Kc = 0.25 at 200 oC.
a) Which direction will the reaction proceed initially?
b) How many grams of calcium carbonate are there in the container at
equilibrium?
Reactions Review
 A reaction occurs when a lump of lead is added to an acidic solution of
potassium dichromate. Write a balanced net ionic equation.
 An environmental engineer wants to remove chromium ions from a
tailings pond by adding a sodium sulfide solution to the tailings pond
solution containing chromium (III) nitrate.
a) Write a balanced net ionic equation for the anticipated reaction above.
b) If 475.0 kg of sodium sulfide is added to the solution containing
chromium (III) nitrate, how many kilograms of the chromium can be
removed from the solution?
 Write a balanced net ionic equation for the reaction that takes place
when carbon dioxide gas is bubbled into water.