Unit 7 Thermodynamics Study Guide Chapters 5 and 19

Unit 7 Thermodynamics Study Guide
Chapters 5 and 19
1. How can thermodynamics and chemical kinetics be shown with a reaction coordinate or profile?
2. What is the major difference between chemical kinetics and chemical thermodynamics?
3. If the definition of spontaneous laughter is “laughing without apparent external cause”, then how does the term
spontaneous apply to physical and chemical processes?
4. Define the following terms and what symbol is used to indicate each.
a. Energy
i. Internal Energy
ii. Enthalpy
iii. Entropy
iv. Free energy
b. Work
c. Heat
5. Which of the above are state functions? Explain
6. What is the 1st law of thermodynamics? (aka-How are energy, heat and work related to each other)
a. How the above concepts are related in a constant volume or constant pressure situations?
7. Compare and contrast an exothermic reaction with an endothermic reaction
8. Compare and contrast “coffee cup” calorimetry, with “bomb”calorimetry.
a. How does a q value obtained in calorimetry become a ΔH value?
9. How can enthalpy changes be calculated by using …..
a. Hess’s Law
b. Standard Enthalpy Formations ( Hf )
i. What does the superscript o indicate about the conditions for that substance?
ii. A substance has a large negative number for Hf . What does this indicate about the stability of
that substance?
iii. A substance has a large positive number for Hf . What does this indicate about the stability of
that substance?
10. Compare and contrast the molar heat of combustion of alkanes and alcohols using a chart of molar heat of
combustions.
11. E85 fuel is a mixture of ethanol and octane. How do these two organic compounds compare and why are there
differences in terms of ….
a. structural or line angle formula
b. molar heat of combustion
c. boiling point
d. octane rating
12. What is the second law of thermodynamics?
a. How can changes in entropy be predicted by using the states of matter and/or the coefficients from a
balanced chemical equation?
13. What is the third law of thermodynamics?
14. Use positional probability to explain why gases have more entropy than a liquid or solid.
15. Use positional probability to explain why solutions have more entropy than there constituent counter parts.
16. Will the entropy change for each of the following be positive or negative? Explain your choice
a. Moisture condenses on the outside of a cold glass. (+ / -)
b. Raindrops form in a cloud. (+ / -)
c. Gasoline vaporizes in the carburetor of an automobile engine. (+ / -)
d. Air is pumped into a tire. (+ / -)
e. Frost forms on the windshield of your car. (+ / -)
f. Sugar dissolves in coffee. (+ / -)
17. Predict the algebraic sign of the entropy change for the following reactions? Explain your choice
a. PCl3(g) + Cl2(g) ----> PCl5(g)
b. SO2(g) + CaO(s) -----> CaSO3(s)
c. CO2(g) + H2O(l) ----> H2CO3(aq)
d. Ni(s) + 2 HCl(aq) -------> H2(g) + NiCl2(aq)
18. What is Gibb’s Free Energy Equation and what can it tell us about a physical or chemical process?
a. How can knowing the sign values of ΔH and ΔS allow you to predict the spontaneity of a process?
i. What influence does temperature have on ΔG?
b. How can ΔG be calculated?
c. Using ΔG, ΔH and ΔS to explain why ice freezes spontaneously below 0oC and melts above 0oC
d. When solid potassium iodide is dissolved in water, a cooling of the mixture occurs because the solution
process is endothermic for these substances. Explain, in terms of what happens to the molecules and ions,
why this mixing occurs spontaneously?
19.
20.
21.
22.
23.
24.
25.
26.
27.
28.
29.
Cu2O: Gof = -146.0, Hof = -168.8
HgO:
Gof = -58.5, Hof = -90.8
PbO:
Gof = -187.9, Hof = -217.3
ZnO:
Gof = -318.4, Hof = -348.3
o
Consider the G f (kJ/mole) and Hof (kJ/mole) for the following oxides shown above. Which oxide can be most
easily decomposed to form the metal and oxygen gas? Explain your choice.
What is the relationship between free energy and work?
What are Keq, Eo and Q? How does these three concepts relate to ΔG? What equations found the AP Chemistry
equation sheet allow you to mathematically solve for these variable when knowing the other variable?
Calculate So (in J/K) for the following reactions.
a. CaO(s) + 2 HCl(g) ---> CaCl2(s) + H2O(l)
b. C2H4(g) + H2O(g) ---> C2H5OH(l)
Phosgene, COCl2, was used as a war gas during World War I. It reacts with the moisture in the lungs to produce HCl,
which causes the lungs to fill with fluid, leading to death of the victim. COCl2 has a standard entropy, So =284 J/mol
K and Ho =-223 kJ/mol. Calculate the Go for COCl2(g) in kJ/mol at body temperature (37 oC).
Aluminum oxidizes forms rather easily, but forms a thin protective coating of Al2O3 that prevents further oxidation
of the aluminum beneath. Use the data for Hfo and So to calculate Go for Al2O3(s) in kJ/mol.
Calculate Go in kJ for the following reactions, using the appropriate data tables. Use Go = Gproducts - Greactants
a. Ca(s) + 2 H2SO4(l) ----> CaSO4(s) + SO2(g) + 2 H2O(l)
Calculate Go (kJ/mole) at 58oC for a reaction with Keq = 3.11 x 102.
The Gof for the formation of NO is 86.7 kJ/mole (2 NO(g)
N2(g) + O2(g)). Calculate Kp for the following reaction
o
at 43 C.
The Kp = 0.106 atm at 25oC for the following reaction. Calculate Go (kJ).N2O4(g)
2 NO2(g)
o
Using the listed information calculate Kp at 25 C for the reaction Ag2O(s)
2 Ag(s) + 1/2 O2(g)
o
o
H f (kJ/mole) -31.0, 0.0, 0.0; S (J/K.mole) 121.3, 42.6, 205.1