Unit 7 Learning Log
1- The equilibrium constant for :
HClO2(aq)  H+ + ClO2-1
Is K = 1.1 x 10-2 at 25C
(a) What is K if the reaction is multiplied by a factor of ½
(b) What is K if the reaction is multiplied by a factor of 2
( c ) What is K if the reverse reaction is multiplied by a factor of 2
2- A mixture of 0.2000 mol of CO2 , 0.1000 mol of H2 , and 0.1600 mol of H2O is placed in a 2.00
L vessel and equilibrium is established at 500 K.
CO2(g) + H2(g)  CO(g) + H2O(g)
At equilibrium, PH20 = 3.51 atm. (a) Calculate the partial pressures of all species at equilibrium
(b) Calculate Kp for the reaction
3- At 80C, Kp = 2.4 x 10-2 for the following reaction:
PH3BCl3 (s)  PH3(g) + BCl3(g)
(a) Calculate the partial pressures of all species if a solid sample of PH3BCl3 is placed in a closed
vessel and allowed to decompose until equilibrium is reached (b) If the flask has a volume of
0.500 L , what is the minimum mass of solid that must be added to achieve equilibrium?
4-Consider the following equilibrium:
2SO2(g) + O2(g)  2SO3(g) Exothermic
How will the following changes affect the equilibrium mixture of the gases
(a) O2 is added to the system
(b) the reaction is heated
(c ) the volume of the reaction vessel is doubled
(d) a catalyst is added
(e) the total pressure is increased by adding Kr
(f) SO3 is added to the system
5- Both the forward and reverse reactions of the following equilibrium are believed to be
elementary steps:
CO(g) + Cl2(g)  COCl(g) + Cl(g)
At 25C, the rate constants for the forward and reverse reactions are 1.4 x 10 -28M-1s-1 and 9.3 x
1010M-1s-1 (a) calculate the equilibrium constant (b)Are reactants or products more plentiful?
Explain
6- When 2.00 mol of SO2Cl2 is placed in a 2.00 L flask at 303K , 56% of the SO2Cl2 decomposes to
SO2 and Cl2 . Calculate Kp for the reaction at this temperature.
7- Sulfuryl chloride, SO2Cl2, is a highly reactive gaseous compound. When heated, it
decomposes as follows:
SO2Cl2(g) < == > SO2 (g) + Cl2(g)
This decomposition is endothermic. A sample of 3.509 grams of SO2Cl2 is placed in an
evacuated 1.00 liter bulb and the temperature is raised to 375 K.
a) What would be the pressure in atmospheres in the bulb if no dissociation of the SO2Cl2 (g)
occurred?
b) When the system has come to equilibrium at 375 K, the total pressure in the bulb is found
to be 1.43 atmospheres. Calculate the partial pressures of SO2, Cl2 and SO2Cl2 at
equilibrium at 375 K.
c) Give the expression for the equilibrium constant (either Kp or Kc) for the decomposition of
SO2Cl2 at 375. Calculate the value of the equilibrium you have given, and specifiy its units.
d) If the temperature were raised to 500 K, what effect would this have on the equilibrium
constant? Explain briefly.
NH4Cl (s) < == > NH3(g) + HCl (g)
 = + 176 kj
8-) Suppose the substances in the reaction above are at equilibrium at 600 K in volume V and
pressure P. State whether the partial pressure of NH3 (g) will have increased, decreased, or
remained the same when equilibrium is reestablished after each of the following disturbances
of the original system. Some solid NH4Cl remains in the flask at all times. Justify each answer
with a one or two sentence explanation.
a)
b)
c)
d)
e)
A small quantity of NH4Cl is added.
The temperature of the system is increased.
The volume of the system is increased.
A quantity of gaseous HCl is added
A quantity of gaseous NH3 is added.
PCl3 (g) + Cl2 (g) < == > PCl5 (g)
9- In the equation above, the forward reaction is first order in both PCl3 and Cl2 and the reverse
reaction is first order in PCl5.
a) Suppose that 2 moles of PCl3 and 1 mole of Cl2 are mixed in a closed container at constant
temperature. Draw a graph that shows how the concentration of PCl3, Cl2, and PCl5 change
with time until after equilibrium has been firmly established.
b) Give the initial rate law for the forward reaction.
c) Provide molecular explanation for the dependence of the rate of the forward reaction on
the concentration of the reactants.
d) Provide a molecular explanation for the dependence of the rate of the forward reaction on
temperature.
e) If this reaction is exothermic, what will happen to the pressure of PCl5 when the
temperature is raised?
10- At elevated temperatures, SbCl5 gas decomposes into SbCl3 and Cl2 gas, as shown by the
following equation.
SbCl5 (g) < == > SbCl3(g) + Cl2 (g)
a) An 89.7 gram sample of SbCl5 (molecular weight 299.0 ) is placed in an evacuated 15.0 L
container at 182oC.
1) What is the concentration in moles per liter of SbCl5 in the container before any
decomposition occurs?
2) What is the pressure in atmospheres of SbCl5 in thte container before any
decomposition occurs?
b) If the SbCl5 is 29.2 percent decomposed when equilibrium is established at 182oC,
calculate the value for the Kc for this decomposition reaction.
c) In order to produce some SbCl5, a 1.00 mole sample of SbCl3 is first placed in an empty 2.00
liter container maintained at a temperature different from 182 oC. At this temperature Kc
equals 0.117. How many moles of Cl2 must be added to this container to reduce the
number of moles of SbCl3 to 0.700 moles at equilibrium
11- At 25o C, Kp= 5.3 x 105 for the reaction
N2 (g) + 3H2 (g) ↔ 2NH3 (g)
When a certain partial pressure of NH3 (g)is put into an empty rigid vessel at 25o C, equilibrium
is reached when 50.0 % of the original ammonia has decomposed. What was the original
partial pressure of ammonia before any decomposition takes place.