Thermodynamics Review
1.
If a process is both endothermic and spontaneous, then
b)
∆H < 0.
c)
∆G > 0.
d)
∆S > 0.
e)
∆H = 0.
2. Is the following reaction spontaneous under standard conditions? Prove your answer.
a. Ba(s) + H2O(g) → BaO(s) + H2(g)
∆G= -291 kJ/mol-rxn Spontaneous
3. Which substance has a higher entropy: SnCl4(l) or SnCl4(g)?
4. A 13.8 g piece of zinc was heated to 98.8 oC in boiling water and then dropped into a beaker
containing 45.0 g of water at 25.0 oC. When the water and metal come to thermal equilibrium, the
temperature is 27.1 oC. What is the specific heat capacity of zinc? 0.400 J/g*oC
5. A 450.8 g sample of water is heated from 5.0 oC to 45.0 oC. How many joules of energy were
absorbed by this sample of water? 75,000 J
6. Predict the sign of ∆So for the following reactions
a. I2(s) + Br2(l)  2 IBr(g)
positive
b. C2H2(g) + 2H2(g)  C2H6(g)
negative
c. N2O(g) + NO2(g)  3 NO(g)
positive
7. Use the following reaction and the data from the appendix in your book to answer the following
questions.
2 PbO(s) + N2(g)  2Pb(s) + 2NO(g)
o
a. ∆H =619.38 kJ/mol-rxn , ∆So= 226.52 J/K and ∆Go =-205.4 kJ/mol for the reaction under
standard conditions (25oC and 1 atm)
b. Interpret the values for ∆Ho, ∆So, and ∆Go by explaining what they tell about the reaction.
i. The reaction is endothermic, spontaneous, product-favored, and decreases
organization.
c. Is the reaction product-favored at 110 oC? No, ∆G=532 kJ/mol-rxn
d. Is the reaction spontaneous at all temperatures? The reaction will be spontaneous at high
temperature only
8. Calculate H for the reaction: C2H4 (g) + H2 (g) --> C2H6 (g), from the following Data.
∆H=-137 kJ/mol-rxn
C2H4 (g) + 3 O2 (g) --> 2 CO2 (g) + 2 H2O (l)
H = -1411. kJ
C2H6 (g) + 3½ O2 (g) --> 2 CO2 (g) + 3 H2O (l)
H = -1560. kJ
H2 (g) + ½ O2 (g) --> H2O (l)
H = -285.8 kJ
9. Calcium carbide, CaC2, is manufactured by the reaction of CaO with carbon at a high temperature.
CaO(s) + 3 C(s) → CaC2(s) + CO(g)
∆H=464.8 kJ/mol-rxn
a. Is this reaction exothermic or endothermic?
b. What is the enthalpy change (heat produced) if 10.0 g of CaO is allowed to react with an
excess of carbon? 82.9 kJ
Thermodynamics Review