Review Focus 4 & 5
Chemistry 200
Name:
1. An ideal gas in a cylinder was placed in a heater and gained 6.30 kJ of energy as heat. If the
cylinder increased in volume from 423 mL to 895 mL against an atmospheric pressure of 690.
Torr during this process, what is the change in internal energy of the gas in the cylinder?
2. A constant-volume calorimeter was calibrated by carrying out a reaction known to release
4.23 kJ of heat in 0.300 L of solution in the calorimeter, resulting in a temperature rise of
6.22°C. Next, 150. mL of 0.20 M HBr(aq) and 150. mL of 0.20 M KOH(aq) were mixed in
the same calorimeter and the temperature rose by 5.61°C. What is the change in the internal
energy of the neutralization reaction?
3. A piston confines 0.963 mol He(g) in 1.7L at 25ºC. Two experiments are performed. (a) The
gas is allowed to expand through an additional 2.5L against a constant pressure of 1.230 atm.
(b) The gas allowed to expand reversibly and isothermally to the same final volume. Which
process does more work?
4. For the following reaction: C3H6O(l) + 4O2(g)→ 3CO2(g) + 3H2O(g)
If 1790 kJ of heat energy is released per mole of acetone (C3H6O):
a) What is the enthalpy of this reaction if 5.75 g of acetone reacts?
b) Find the enthalpy of reaction when sufficient acetone is burned to produce 0.79 mole
of carbon dioxide?
Dr. Behrang Madani
Chem 200
IVC
5. Calculate Ho for the reaction:
CH4(g) + 4Cl2(g)  CCl4(g) + 4HCl(g)
given the following information:
Ho
(1) C(s) + 2H2(g)  CH4(g)
-74.6 kJ
(2) C(s) + 2Cl2(g)  CCl4(g) -95.7 kJ
(3) H2(g) + Cl2(g)  2HCl(g) -92.3 kJ
6. Calculate Horxn for the following reaction at 25.0 oC:
Fe3O4(s) + CO(g)  3FeO(s) + CO2(g)
o
-110.5 -272
-393.5
Hf (kJ/mol) -1118
7. How much heat is required to convert a 35.0-g block of ice at -3.74ºC into water vapor at
210.3ºC. Use the information in Appendix 2.
Dr. Behrang Madani
Chem 200
IVC
8. Suppose that 2.30 mol of ideal gas molecules at 389 K at 2.00 atm expands from 5.30 L to
18.90 L and has a final pressure of 0.964 atm. Find the amount of work by two different paths.
(a) Path A is an isothermal, reversible expansion.
(b) Path B has two parts. In step 1, the gas is cooled at constant volume until its pressure has
fallen to 0.964 atm. In step 2, it is heated and allowed to expand against a constant pressure of
0.964 atm until its volume is 18.90 L and T = 389 K. Determine for each path the work done,
the heat transferred, and the change in internal energy (w, q, and ΔU).
9. In an endothermic reaction at constant pressure, 55. kJ of energy entered the system as
heat. The products took up less volume than the reactants, and 65. kJ of energy entered the
system as work as the outside atmosphere pressed down on it. What are the values of (a) ΔH
and (b) ΔU for this process?
10. Write the equilibrium expression for the follwoing equations:
a) 2KclO3(s) ⇌ 2KCl(s) + 3O2(g)
b) 2NOBr(g) ⇌ 2NO(g) + Br2(g)
c) NH4HS(s) ⇌ NH3(g) + H2S(g)
d) Ag2SO4(s) ⇌ 2Ag+(aq) + SO42-(aq)
Dr. Behrang Madani
Chem 200
IVC
11. At a given temperature, an equilibrium mixture of the reaction 2C(s) + O2(g) ⇌ 2CO(g)
contains 12.86 g O2, and 16.93 g of CO in a 4.10 liter container. Imagine the concentration of
C remains constant. Find the value of K.
12. The following system is at equilibrium. In which direction (right or left) will the equilibrium
position shift with the following changes? This reaction is an endothermic reaction.
C(s) + H2O(g) ⇌ CO(g) + H2(g)
a) Adding more H2O
b) Removing some H2
c) Adding more CO
d) Lowering the temperature
e) Raising the temperature
f) Adding a catalyst
g) Increasing the volume
13. At 56°C, the equilibrium constant Kc for the fowling reaction is 8.5×10-3.
NH4HS(s) ⇌ NH3(g) + H2S(g)
What is the value of Kp at this temperature?
Dr. Behrang Madani
Chem 200
IVC
14. Calculate the value of Kc for the reaction: C(g) + H2O(g) ⇌ CO(g) + H2(g), using the
following information.
Equation
(a) C(g) + O2(g) ⇌ CO2(g)
(b) 2H2(g) + O2(g) ⇌ 2H2O(g)
(c) 2CO(g) + O2(g) ⇌ 2CO2(g)
Equilibrium Constant
Kc = 1.363 x 1069
Kc = 1.389 x 1080
Kc = 1.477 x 1090
15. For the following reaction,
N2(g) + 3H2(g) ⇌ 2NH3(g)
The equilibrium constant KC = 0.0584 at 775K. What are the equilibrium concentration of H2,
N2, and NH3 if the concentration of N2 is 0.265M and H2 is 0.860M at the beginning (at
775K)? Imagine Kp has very small value.
16. Consider the following reaction: 2SO3(g) ⇌ 2SO2(g) + O2(g), starting with 1.5 bar SO3 it
was found at equilibrium that the pressure of SO2 was 0.06 bar and the pressure of O2 was
0.03 bar. What is the final pressure of SO3? Calculate Kp.
Dr. Behrang Madani
Chem 200
IVC