Chemistry 12 Equilibrium Review
Part 1 Relationships
1. Describe the changes in reactant and product concentration as equilibrium is approached.
2. Describe the changes in the forward and the reverse rates as equilibrium is approached.
3. State three conditions that are necessary to achieve equilibrium.
4. Asuming all three conditions are present, describe what would happen if only reactants are placed in a container.
5. Asuming all three conditions are present, describe what would happen if only products are placed in a container.
6. Describe the relationship between the size of the equilibrium constant, large, small, or about 1, and the relative amounts of reactants or products.
7. Describe each of the following: dynamic equilibrium, LeChatelier's principle, Ktrial, enthalpy, entropy and macroscopic property.
8. Describe the effect of temperature on the equilibrium constant for an exothermic and endothermic reaction.
9. Describe the effect of changing the temperature, pressure , volume, concentration or adding a catalyst on the value of the equilibrium constant.
10. What is the only variable that will change the value of the equilibrium constant.
11. What are the phases of the compounds that are not included in the equilibrium expression.
12. Write the equilibrium expession for:
4A(g) + 3B(aq) <------> 2C(l) + 3D(s)
13. Pick the best Keq for each of the reactions below.
Keq = 100 Keq = 0.01 Keq = 1.0
a) Zn(s) + 2HCl(aq) ------> ZnCl2(aq) + H2(g) + 152kJ
b) 3C(s) + 3H2(g) ------> C3H6(g) ÆH = +20.4 kJ
c) 2Pb(NO3)2(s) + 597 kJ ------> 2PbO(s) +4NO2(g) + O2(aq)
14. For each reaction in equilibrium describe the shift for the following changes: increasing temperature, increasing pressure, decreasing volume, adding a gaseous product and removing an aqueous reactant.
a) Zn(s) + 2HCl(aq) <------> ZnCl2(aq) + H2(g) + 152kJ
b) A(aq) + 6B(g) <------> 2C(g) + 4D(g) ÆH= +56kJ
15. Zn(s) + 2HCl(aq) <------> ZnCl2(aq) + H2(g) + 152kJ
Give three ways to increase the yield of the reaction.
Give five ways to increase the rate of the reaction.
16. A(aq) + 6B(g) <------> 2C(g) + 2D(g) ÆH= +56kJ
Give three ways to increase the yield of the reaction.
Give five ways to increase the rate of the reaction.
17. What is equal at equilibrium?
18. What is constant at eqilibrium?
19. Which reaction has the greatest yield? Why?
a) Keq = 8.0 x 10-12 b) Keq = 7.0 x 10-11
20. Which reaction has the smallest yield?
a) Keq = 1.0 x 10-15 b) Keq = 9.0 x 10-15
21. Which has the greater entropy?
a) H2O(s) b) H2O(l) c) H2O(g)
22. Which has the greater enthalpy?
a) H2O(s) b) H2O(l) c) H2O(g)
Hint: Consider H2O(s) ----> H2O(l) Draw a potential energy diagram. Which side is higher?
23. Review your kinetics test. There will be 5 question on this test from kinetics.
24. Consider the following equilibrium system:
SO3(g) + NO(g) <----> NO2(g) + SO2(g)
a) Describe what happens to the forward and reverse reaction rate immediately after adding SO3(g)
b) Describe what happens to the forward and reverse reaction rate immediately after removing NO2(g)
c) Describe what happens to the forward and reverse reaction rate immediately after adding a catalyst .
d) Describe what happens to the forward and reverse reaction rate after a new equilibrium has formed compared to the original equilibrium after removing NO2(g)
e) Describe what happens to the forward and reverse reaction rate after a new equilibrium has formed compared to the original equilibrium after adding SO3(g)
f) Describe what happens to the forward and reverse reaction rate after a new equilibrium has formed compared to the original equilibrium after adding a catalyst .
g) Describe what happens to the forward and reverse reaction rate after a new equilibrium has formed compared to the original equilibrium after decreasing the volume of the container.
h) Describe what happens to the reactant and product concentrations after a new equilibrium has formed compared to the original equilibrium after decreasing the volume of the container.
Part 2 Calculations
1. SO3(g) + NO(g) <----> NO2(g) + SO2(g)
[SO3] = 0.400M [NO] = 0.480M [NO2] = 0.600M [SO2] = 0.450M
Keq = 0.800 at 100ºC
a) Show by calulation that this reaction mixture is not at equilibrium at 100ºC.
b) What will happen to [SO3] and [SO2] as the system moves to equilibrium?
2. Consider the equilibrium below:
Co(H2O)6+2(aq) + 2Cl-1(aq) <-----> Co(H2O)6Cl2(aq) + 2H2O(l)
(pink blue)
If the colour of the equilibrium mixture is pink at 5ºC and blue at 60ºC, is the reaction endo or exothermic?
3. SO3(g) + H2O(g) <----> H2SO4(l)
[SO3] = 0.400M [ H2O] = 0.480M [H2SO4] = 0.600M
Calculate the value of the equilibrium constant.
4. 2SO2(g) + O2(g) <-----> 2SO3(g)
4.00 moles of SO2 and 5.00 moles O2 are placed in a 2.00 L container at 200ºC and allowed to reach equilibrium. If the equilibrium concentration of O2 is 2.00M, calculate the Keq.
5. 2SO2(g) + O2(g) <-----> 2SO3(g)
If at equilibrium [O2] =.500M and [SO3] = .400M and the equilibrium constant is the same as question 4 at 200ºC , calculate the [SO2].
6. Consider the following equilibrium:
2NO2(g) <-----> N2O4(g)
If 2.00 moles of NO2 are placed in a 1.00 L flask and allowed to react. At equilibrium 1.80M NO2 are present. Calculate the Keq.
7. SO3(g) + NO(g) <----> NO2(g) + SO2(g) Keq = 0.800 at 100ºC
If 4.00 moles of each reactant is placed in a 2.00L container, calculate all equilibrium concentrations at 100ºC.
8. Keq = 0.0183 at 150ºC for : 2HI(g) <----> H2(g) + I2(g)
If 3.00 moles of HI is placed in a 5.00 L container and allowed to establish equilibrium, what are all equilibrium concentrations?
Challenge Question
9. Consider the following equilibrium in a 5.00 L container:
CO (g) + H2O (g) <---------> CO2(g) + H2 (g)
At equilibrium, there is 1.0 mole of CO , 3.0 moles of H2O, 3.0 moles CO2, and 3.0 moles of H2. If 2.0 moles of CO are now added, find the equilibrium [CO2].