Untitled - Kelly Walsh High School

Entropy and Free Energy 263
ANSWER KEY
1. The first law of thermodynamics states that the total energy of the universe
is constant. The second law of thermodynamics states that all processes that
occur spontaneously move in the direction of an increase in entropy of the
universe (system surroundings). The third law of thermodynamics states
that for a pure crystalline substance at 0 K the entropy is zero.
2. a 3. negative 4. G = H TS
5. If Ssurroundings is sufficiently positive to make the total entropy change positive,
the process will be spontaneous.
6. Standard conditions are: 25°C (298 K), 1 atm, and 1 M.
7. G G° + RT ln Q 8. G° RT ln K 9. R 8.314 J/molK
10. The setup of K and Q is the same. K uses equilibrium quantities, whereas
Q uses nonequilibrium, often initial, quantities.
11. In both cases, the values are zero.
12. ∆S [(1 mol CaSO42H2O)(194.0 J/molK] [(1 mol Ca)(41.63 J/molK)
(1 mol S)(31.88 J/molK) (2 mol H2)(131.0 J/molK)
(3 mol O2)(205.0 J/molK)]
∆S 757 J/K
13. ∆G [(1 mol CaSO4)(1320.3 kJ/mol) (2 mol H2O)(237.2 kJ/mol)
(1 mol SO2)(300.4 kJ/mol)] [(1 mol Ca)(0.00 kJ/mol)
(2 mol H2SO4)( 689.9 kJ/mol)]
∆G 715.3 kJ
14. T 3.30 102 K
15. ∆G (298 K) ln (1.9 1016 ) 8.97 104 8.314 J
a J/mol
mol·K b
(31.9 kJ/mol) (10
(96.8 J/mol·K)
3 H
J)
S
(1 kJ)
[2.50] 2
16. ∆G 120.0 kJ (8.314 J/molK)(298 K) a ln 123.5 kJ
[1.50]
(Note: Do not forget to ignore the solid.)
1kJ
103 J b