Part 1--Equilibrium Practice
1)
HI reacts according to the equation: 2 HI (g) ↔ H2 (g) + I2 (g)
At equilibrium, [HI] = 6.8 10−2 M, and [H2] = [I2] = 9.2 10− 3 M.
a. Write the equilibrium constant expression for the reaction.
b. Calculate the value of the equilibrium constant Keq.
2)
Ozone, O3, is a gas that decomposes according to the reaction: 3 O2 (g) ↔ 2 O3 (g)
The Keq for this reaction is 1.0 10− 7 M and the concentration of O2 gas is 2.0 10−1 M.
a. Write the equilibrium constant expression for the reaction.
b. Calculate the equilibrium concentration of O3(g).
3)
At equilibrium the concentration of SO3 gas is 2.61 101 M; the concentration of SO2 gas is 1.2 M; and the
concentration of O2 gas is 1.81 M at a certain temperature for the following reaction:
2 SO2 (g) + O2 (g) ↔ 2 SO3 (g)
a. Write the equilibrium constant expression for the reaction.
b. Calculate the value of the equilibrium constant Keq.
4)
Methanol, can be produced according to the reaction: CO (g) + 2 H2 (g) ↔ CH3OH (g)
At equilibrium, the concentration of CO gas is 0.020 M and the concentration of H2 gas is 0.60 M.
The equilibrium constant for the reaction is 2.2 102.
a. Write the equilibrium constant expression for the reaction.
b. Calculate the equilibrium concentration of CH3OH (g).
5)
Copper(I) chloride dissolves according to the reaction: CuCl (s) ↔ Cu + (aq) + Cl – (aq)
The equilibrium constant for the reaction is 3.2 10–7.
a. Write the equilibrium constant expression for the reaction.
b. Calculate the equilibrium concentration of the copper (I) ion.
c. Calculate the equilibrium concentration of the chloride ion.
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6) Determine the equilibrium constant for the reaction below. At equilibrium the concentration of SO3 gas is 2.61
x 10 1 M; the concentration of SO2 gas is 1.2 M; and the concentration of O2 gas is 1.81 M.
2 SO2 (g) + O2 (g) ↔ 2 SO3 (g)
7) In the equilibrium system CO (g) + 2 H2 (g) ↔ CH3OH (g) the [CO] is 0.020 M; the [H2] is 0.60 M; and the
[CH3OH] is 1.58 M. Determine the K eq for the system.
8) Why does a larger Keq value mean that the reaction is “more successful” or “favors product.” Provide actual
numbers to prove your point.
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Part 2--LE CHATELIER’S PRINCIPLE
For each of the reactions below, indicate with an arrow (right or left) in the box which direction is favored to recreate the
equilibrium position. (Please draw in the remaining boxes for each reaction. The first is an example.) Also indicate with an arrow in
the box what happens to the concentration of each part of the reaction by using an arrow pointing up for increase and an arrow
pointing down for decrease. For the part of the system that was affected by the change, simply write what type of changed
occurred. For example: in reaction 1, just write “add” over H2 (g).
REACTION
1.
C2 H6 (g)
↔
CHANGE
H2 (g)
+ C2H4 (g)
Add H2 (g)
increase
2.
H2 (g) + Cl2 (g) ↔ 2 HCl (g)
Remove H2 (g)
3.
CO (g) + NO2 (g) ↔ CO2 (g) + NO (g)
Remove CO2 (g)
4.
Ag (aq) + Cl (aq) ↔ AgCl (s)
5.
Cu (aq) + 4 NH3 (g) ↔ Cu (NH3)4 (aq)
6.
PbSO4 (s) + H (aq) ↔ Pb (aq) + HSO4 (aq)
Add Pb(NO3)2 solution
7.
CO (g) + 0.5 O2 (g) ↔ CO2 (g) + Energy
Add heat
8.
H2O (l) + Energy ↔ H2O (g)
Remove heat
9.
2 H2 (g) + 2 NO (g) ↔ N2 (g) + 2 H2O (g)
Increase pressure
+
-
++
Add AgCl (s)
++
+
++
Add CuSO4 (s)
-
10.
CO (g) + 2 H2 (g) ↔ CH3OH (g)
Decrease volume
11.
FeO (s) + CO (g) ↔ Fe (s) + CO2 (g)
Remove Fe (s) as produced
12. H2 (g) + Cl2 (g) ↔ 2 HCl (g)
Increase volume
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Part 3--Reaction Kinetics
1. Write the chemical equation to describe the reaction progrss curve shown below:
C
[concentration]
B
A
time
2. Identify the various parts of the potential energy diagram below.
A
energy
D
B
A
C
(theCarrow)
B
D
3. Is the reaction represented by the diagram above endothermic or exothermic? Explain.
2
[M]
C
B
1
A
Time
(sec)
4. Given the graph above
a)
Identify the reactant(s) and the product(s).
b) Identify the initial concentrations of A, B and C.
c)
Identify the final concentrations of A, B, and C.
d) Write the chemical equation that describes this reaction.
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Part 4--Energy Change During a Reaction
Below is a chemical reaction. The shapes represent the shape of the molecules
C
A + B ----- C + D
A
B
D
1. There are 4 regions identified on the graph below. DRAW ON THE GRAPH the molecules as they would appear
for each region on the graph. Write a 1 sentence statement describing what is happening in each of those
regions in terms of energy.
2
3
Potential
Energy
1
4
5
2. Use the potential energy graph below to answer question.
D
60
60
E
F
50
Potential
Energy
(KJ/mol)
40
40
Catalyzed
20
a.
b.
c.
d.
e.
f.
50
C
30
.
G
A
30
B
Reaction Coordinate
20
What letter(s) represent the actual reaction?
____________________
What letter(s) represent the activated complex?
___________________
What is the activation energy for the forward catalyzed reaction? _______________
What is the ΔH rxn for the forward reaction? ___________________
What is the activation energy of the reverse reaction? __________________
What type of thermodynamic reaction is the reverse reaction? _____________
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Part 5-- Kinetic Energy Distribution Graphs
1. A study is done of the speeds of cars on the 56 freeway. Do the following on the graph itself.
a.
b.
c.
d.
Label the axes
Draw what the data would look like
Identify which cars would receive speeding tickets
Sketch what the curve would look like if you made the measurements during a rain storm
Cars on the 56
Speed Limit
2A) The large graph below represents the distribution of KE among the particles of a chemical reaction. The dotted
vertical line shows where the minimum Threshold Kinetic Energy requirement is for the reaction. Molecules must reach
this in order to react. Sketch the curve that would represent the distribution of KE among the population of molecules
in the reaction?
2B) The group of smaller axis below, show the same reaction under different conditions. Sketch what the new curve
location would be based on the effect for the new conditions.
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Number of particles
Energy
Raise Temp
Lower Temp
Raise Pressure
Lower Volume
Add
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Part 6--Concentration Over Time
3. Suppose the above reaction A + B --- C + D is monitored over time for the concentrations. Trace on the graph
below what would happen. Assume the starting concentrations of “A” and “B” are both 2 M and the ending
concentration of “C” and “D” is 1.3 M. NOTE: you should end up with 4 lines drawn on the graph.
4. Explain why the concentration of “C” and “D” does not end up being 2 M and the concentration of “A” and “B” does
not go to zero. Incorporate a potential energy graph to help you explanation.
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