Download Ch 19 test_take-home

Name: _____________________________________
AP Chem Ch 19 Test (take home).
Do your own work. No collaboration. Use book, notes, assigned problems. Use App C data as
necessary. Show all math to receive credit. Underline or put a box around answer.
1) Calculate the value of ΔSo for the combustion of ethane in the presence of excess oxygen.
2C2H6 (g) + 7O2 (g) → 4CO2 (g) + 6H2O (l)
2) Calculate the value of ΔH° for the decomposition of POCl3 into its constituent elements.
2POCl3 (g) → P2 (g) + O2 (g) + 3Cl2 (g)
3) Calculate ΔG° (in kJ/mol) for the following reaction at 1 atm and 25°C:
C2H6 (g) + O2 (g) → CO2 (g) + H2O (l)
4) Calculate the value of ΔG° at 373 °K for the oxidation of solid elemental sulfur to gaseous sulfur dioxide.
S (s, rhombic) + O2 (g) → SO2 (g)
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5) Calculate the equilibrium constant for the reaction below at 25 oC:
2 SO2 (g) + O2 (g)
2SO3 (g)
6) The equilibrium constant for a reaction is 0.48 at 25 °C. What is the value of ΔG° (kJ/mol) at this temperature?
7) Calculate the value of △G° at 100.0 °C for the oxidation of solid elemental sulfur to gaseous sulfur dioxide,
S (s, rhombic) + O2 (g) → SO2 (g)
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8) The given thermodynamic values apply to the reaction below. Calculate the temperature of this reaction in oC.
P2 (g) + 3Cl2 (g) → 2PCl3 (g)
△H° is -720.5 kJ/mol, △G° is -642.9kJ/mol, and ΔS° is -263.7J/K.
9) In the Haber process, ammonia is synthesized from nitrogen and hydrogen:
N2 (g) + 3H2 (g) → 2NH3 (g)
△G° at 298 oK for this reaction is -33.3 kJ/mol. What is the value of △G at 298 K for a reaction mixture that consists
of 1.9 atm N2, 1.6 atm H2, and 0.65 atm NH3?
Circle the correct answer for the following questions:
10) The first law of thermodynamics can be given as __________.
A) ΔE = q + w
nH f (products) mH f (reactants)
B) H rxn =


C) for any spontaneous process, the entropy of the universe increases
D) the entropy of a pure crystalline substance at absolute zero is zero
E) ΔS = qrev/T at constant temperature
11) A reaction that is spontaneous as written __________.
A) is very rapid
B) will proceed without outside intervention
C) is also spontaneous in the reverse direction
D) has an equilibrium position that lies far to the left
E) is very slow
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12) When a system is at equilibrium, __________.
A) the reverse process is spontaneous but the forward process is not
B) the forward and the reverse processes are both spontaneous
C) the forward process is spontaneous but the reverse process is not
D) the process is not spontaneous in either direction
E) both forward and reverse processes have stopped
13) A reversible process is one that __________.
A) can be reversed with no net change in either system or surroundings
B) happens spontaneously
C) is spontaneous in both directions
D) must be carried out at low temperature
E) must be carried out at high temperature
14) The thermodynamic quantity that expresses the degree of disorder in a system is __________.
A) enthalpy
B) internal energy
C) bond energy
D) entropy
15) For an isothermal process, ΔS = __________.
A) q
B) qrev/T
C) qrev
D) Tqrev
E) q + w
16) Which one of the following is always positive when a spontaneous process occurs?
A) ΔSsystem
B) ΔSsurroundings
C) ΔSuniverse
D) ΔHuniverse
17) The entropy of the universe is __________.
A) constant
B) continually decreasing
E) heat flow
C) continually increasing
D) zero
E) ΔHsurroundings
E) variable
18) The second law of thermodynamics states that __________.
A) ΔE = q + w
nH f (products) mH f (reactants)
B) H rxn =


C) for any spontaneous process, the entropy of the universe increases
D) the entropy of a pure crystalline substance is zero at absolute zero
E) ΔS = qrev/T at constant temperature
19) Which one of the following processes produces a decrease in the entropy of the system?
A) boiling water to form steam
B) dissolution of solid KCl in water
C) mixing of two gases into one container
D) freezing water to form ice
E) melting ice to form water
20) For a reaction to be spontaneous under standard conditions at all temperatures, the signs of ΔH° and ΔS° must be __________
and __________, respectively.
A) +, +
B) +, C) -, +
D) -, E) +, 0
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