Thermo Review

Thermo Review
1. What is the E (in J) of a system that releases 12.4 J of heat and does 4.2 J of work on
the surroundings.
2. Which of the following conditions would always result in an increase in E of a
system?
A)
B)
C)
D)
E)
3. A
A)
B)
C)
D)
E)
The system loses heat and does work on the surroundings.
The system gains heat and does work on the surroundings.
The system loses heat and has work done on it by the surroundings.
The system gains heat and has work done on it by the surroundings.
None of these is correct.
 H corresponds to an  process.
Negative, endothermic
Negative, exothermic
Positive, exothermic
Zero, exothermic
Zero, endothermic
4. Which of the following statements is not true regarding enthalpy?
a)
b)
c)
d)
e)
The change in enthalpy is positive for a process that absorbs heat.
Enthalpy is a state function.
Enthalpy is an extensive property.
A change in enthalpy is measured at a constant pressure.
The enthalpy of a system can be measured.
5. For the hypothetical reaction 3X2 (g)  2X3 (g), H is –333 kJ (the atomic weight of
X is 66.6 amu). H for conversion of 11.1g of X3 a gas into X2 gas is  kJ.
6. The value of H for a reaction below is 336kJ. Determine the amount of heat ( in kJ)
exchanged wit the surroundings when 23.0 g of HCl is formed.
CH4 (g) + 3Cl2 (g)  CHCl3 (l) + 3HCl (g)
7. The value of H for the reaction below is –6535kJ. How many kJ of heat are evolved
in the combustion of 16.0g of C6H6 (l)?
2C6H6 (l) +15O2 (g)  12CO2 (g) +6 H2O (l)
8. When a sample of aluminum is absorbed 9.86J of heat, its temperature increased from
23.2 C to 30.5 C. Since the specific heat of aluminum is .90 J/g-K, the mass of the
sample was g.
9. When 29 J of heat is transferred to 15g of lead at 22 C, the temperature of the lead
increases to 37 C. What is the specific heat capacity (J/g-k) of lead?
10. A 1.96 g sample of titanium was burned in a bomb calorimeter that had a heat
capacity of 9.84 kJ/k. The temperature of the calorimeter increased from 36.84C
to98.82C. Calculate the heat (kJ) that is released from the combustion of one mole of
titanium.
11. Consider the following thermochemical equations:
Fe2O3 + 3CO  2Fe + 3CO2 H = -28.0 kJ
3Fe + 4CO2  4CO + Fe3O4 H = +12.5 kJ
Calculate the value of H (in kJ) for:
3Fe2O3 + CO  CO2 + 2Fe3O4
12. Calculate H (in kJ/mol) for:
Ca(OH)2 + 2H3AsO4  Ca(H2AsO4)2 + H2O
Substance
Hf (kJ/mol)
Ca(OH)2
H3AsO4
Ca(H2AsO4)2
H2O
-986.6
-900.4
-2346.0
-258.9
13. The thermodynamic quanity that expresses the degree of disorder in a system is
___________.
a) enthalpy
b) internal energy
c) bond energy
d) entropy
e) heat flow
14. The entropy of the universe is _____________.
a) constant
b) continually decreasing
c) continually increasing
d) zero
e) isotonic
15. Given the following table of thermodynamic data,
Substance
ΔHf°
S°
PCl3 (g)
-288.07 kJ/mol
311.7 J/mol-K
PCl3 (l)
-319.6
217
Determine the normal boiling point (in °C) of PCl3
16. ΔS° will be positive for the reaction ____________.
a) 2H2 (g) + O2 (g)  2H2O (g)
b) 2NO2 (g)  N2O4 (g)
c) H+ (aq) + F- (aq)  HF (aq)
d) BaF2 (s)  Ba2+ (aq) + 2F- (aq)
e) 2Hg (l) + O2 (g)  2HgO (s)
17. Calculate ΔS° for the reaction below at 25°C.
4Al (s) + 3O2 (g)  2Al2O3 (s)
Substance
Al(s)
Al2O3 (s)
O2 (g)
ΔS° (J/mol · K)
28.32
51.0
205.0
18. Consider the following reaction at 25°C.
C(s) + H2O(g)  CO(g) + H2(g)
ΔG° = 91.2 kJ
ΔH° = 131.4 kJ
What is the value of ΔS° (J/K) for this reaction at 25°C.
19. Determine the value of ΔG° (kJ) for the following reaction using data from the table
below.
2H20(g) + O2(g)  2H2O2 (g)
Substance
ΔG°f (kJ/mol)
2H20
-228
H2O2
-105
20. For the Reaction
C2H6(g)  C2H4(g) + H2 (g)
ΔH is 137 kJ and ΔS° is 120 J/K.
This reaction will be
a) spontaneous at all temperatures
b) spontaneous only at high tempratures
c) spontaneous only at low tempratures
d) nonspontaneous at all tempratures
e) unreliable
21. for a reaction to be spontaneous at all tempratures, the signs of ΔH° and ΔS° must be
___________ and ___________, respectively.
a) +, +
b) +, c) -,+
d) -, e) +, 0