CHM 2046C Name: ________________

Module 13 Paper and Pencil Homework Packet

Module Thirteen: Thermochemistry II McMurry Chapter 16	Possible	Actual
A. Laws of Thermodynamics Chapters 8,16	5	Answers
B. Entropy: Disorder & Spontaneity	5	Answers
C. Calculation Standard Entropy of Reaction	5	Answers
D. Derivation of Gibbs Equation	5	Answers
E. Free Energy: Spontaneous Change Calculations	5	Answers
F. Free Energy:Calculation Problems	5	Answers
G. Calculation Free Energy from Standard Free Energy of Formation	5	Answers
H.Calculation of Equilibrium Constant from Standard Free Energies of Formation	5	Answers
K. Key Terms Chapter 16	5	Answers
Module Thirteen Total:	45

Part A. Laws of Thermodynamic 5 points

1. Describe the difference between Thermodynamics and Kinetics of a chemical reaction.

2. What two components drive a naturally occurring process? Explain their relationship to a spontaneous process.

3. What do you understand by the word “entropy”?

4. State the First Law of Thermodynamics.

.

5. State the Second Law of Thermodynamics.

.

6. State the Third Law of Thermodynamics.

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Part B Entropy: Disorder and Spontaneity 5 points

1. What six types of processes or reactions lead to an increase in entropy?

2. How are entropy, enthalpy, and the spontaneity of a reaction related?

The reaction is spontaneous if ___________________________.

The possibilities are:

∆H^osys	∆S^osys	Result
(exothermic)
(exothermic)
(endothermic)
(endothermic)

3. Which of the following processes are spontaneous and which are nonspontaneous:

(a) diffusion of perfume molecules from one side of the room to the other.

(b) Heat flow from a cold piece of metal (2^oC)to hot water(70^oC) when the cold metal is dropped into the hot water.

(c) Decomposition of rust (Fe₂O₃∙H₂O) to iron metal, oxygen gas, and water.

(d) Decomposition of solid CaCO₃ to solid CaO and gaseous CO₂ at 25^oC and 1 atm pressure (K_p = 1.4 x 10 ^-23)

4. Predict the sign of ∆S in the system for each of the following processes:

(a) CO₂ (s) ---> CO₂ (g) (sublimation of dry ice)

(b) CaSO₄(s) ---> CaO(s) + SO₂(g)

(c) N₂(g) + 3 H₂ (g) ---> 2 NH₃ (g)

(d) I₂(s) ---> I₂ (aq) (dissolution of iodine in water)

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Part C: Calculating Standard Entropy of Reaction 5 points

Calculate the standard entropy of reaction at 25^oC for the Haber Process of ammonia:

N₂ (g) + 3 H₂ (g) à 2 NH₃ (g)

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Part D: Derivation of Gibbs Free Energy Change & Discussion: 5 points

The quantity called the Gibbs free-energy change (∆G),

∆G = ∆H - T∆S, determines whether a chemical or physical process will occur spontaneously. Fill in the following:

∆G < 0 Process is _______________________________________________

∆G = 0 Process is _______________________________________________

∆G > 0 Process is _______________________________________________

This quantity: ∆G = ∆H - T∆S is derived from the following equation:

∆S^o_universe = ∆S^o_system + ∆S^o_surroundings

Show this derivation with stepwise explanations/comments:

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Part E: Reaction Spontaneity Calculation: 5 points

The quantity called the Gibbs free-energy change (∆G),

∆G = ∆H - T∆S, determines whether a chemical or physical process will occur spontaneously. Iron metal can be produced by reducing Iron III oxide (rust) with Hydrogen:

Fe₂O₃ (s) + 3 H₂ (g) ---> 2 Fe (s) + 3 H₂O (g) ∆H^o = +98.8 kJ;

∆S^o = +341.5 kJ/K

(a) Is this reaction spontaneous under standard state conditions at 25^oC?

At what temperature will the reaction be become spontaneous?

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Part F: Calculation ∆G^o from ∆H^o and ∆S^o 5 points

Using the quantity called the Standard Gibbs free-energy change (∆G^o),

∆G^o = ∆H^o - T∆S^o,

perform the following calculations using values in Appendix B:

Iron metal is produced commercially by reducing Iron III oxide in iron ore with

Carbon monoxide:

Fe₂O₃ (s) + 3 CO (g) ---> 2 Fe (s) + 3 CO₂ (g)

(b) Calculate the standard free-energy change for this reaction at 25^oC?

(c) Is the reaction spontaneous under standard conditions at 25^oC?

(d) Does the reverse reaction become spontaneous at higher temperature? Explain.

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Part G: Calculation of ∆G^o Values from ∆G^o_f Values 5 points

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Part H: Calculation of an Equilibrium Constant from ∆G^o Values

5 points

See Table 16.4 page 673; and worked example 16.9 page 673:

Methanol (CH₃OH, an important alcohol used in the manufacture of adhesives, fibers, and plastics, is synthesized industrially by the reaction:

CO (g) + 2 H₂ (g) ↔ CH₃OH (g)

Use the thermodynamic data in Appendix B (values below) to calculate the equilibrium constant for the reaction at 25^oC.

Additional Values from Appendix B:

∆G^o_f CO = 51.3 kJ/mol

∆H^o_f CO = -110.5 kJ/mol

S^o CO = 197.6 J/K∙mol

S^o H₂ = 130.6 J/K∙mol

∆G^o_f CH₃OH = -166.4 kJ/mol

∆H^o_f CH₃OH= -201.2 kJ/mol

S^o CH₃OH= 238 J/K∙mol

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Part K: Chapter 16 Key Terms 5 points

1. _____________ – the amount of molecular randomness in a system

2. _________________ – The total internal energy of an isolated system is constant.

3. _________________ –. A thermodynamic state function relating enthalpy, temperature, and entropy

4. ___________________ - In any spontaneous process, the total entropy of a system and its surroundings always increases..

5. ___________________ – a process that proceeds on its own without any continuous external influence

6. ___________________ – entropy change under standard state conditions

7. __________________-:The free-energy change for formation of

1 mol of a substance in the standard state from the most stable form of the constituent elements in their standard states. :

8. ___________________ – the entropy of one mole of a pure substance at 1 atm pressure and a specific temperature, usually 25^oC for a gas, 1 M concentration for a solution

9. ___________________ The most stable form of an element or compound in the physical state in which it exists at 1 bar and the specific temperature. `.

10. _________________ – the study of the interconversion of heat and other forms of energy

11. ___________________ The entropy of a perfectly ordered crystalline substance at Zero Kelvin (0 K) is Zero

Review Terms:

12. __________________– the heat change in a reaction or process at constant pressure ∆H = ∆E + P∆V

13. __________________– The substance being evaluated for energy content in a thermodynamic process.

14. __________________ – everything outside the system in a thermodynamic process

15. __________________- a reaction in which heat is evolved and the temperature of the surroundings rises

16. __________________- a reaction in which heat is absorbed and the temperature of the surroundings falls

17. __________________– a quantity whose value is determined only by the state of the system

18. __________________ – the enthalpy change for the hypotheorical formation of 1 mol of a substance in the stanbdard state from the most stable forms of it constituent elements in their standard states.

19. _____________________Heat flows into or out of a thermodynamic system so that there is no temperature chane in the system.

20. _____________________No heat may flow into or out of a thermodynamic system. The system is perfectly insulated from its surroundings