CHM 2046C                                       Name: ________________

Module 13 Paper and Pencil Homework Packet




8Module Thirteen: Thermochemistry II Jespersen Chapter 18



A.   Laws of Thermodynamics Sections 18.1; 18.4; 18.5  



B.   Entropy: Disorder & Spontaneity Section 18.3



C.  Calculation Standard Entropy of Reaction  18.6                                  



D.  Derivation of Gibbs Equation



E.   Free Energy: Spontaneous Change Calculations Section18.8



F.   Free Energy Calculation Problems Section 18.8



G. Calculation Free Energy from Standard Free Energy of Formation Section 18.8



H.Calculation of Equilibrium Constant from Standard Free Energies of Formation Sect 18.8



8K.   Key Terms Chapter 16



Module Thirteen Total: 




Part A.  Laws of Thermodynamic     1 point


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






  1. 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        1 point


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:

















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 (2oC)to hot water(70oC) 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 25oC and 1 atm pressure (Kp = 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             1  point


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


                                     N2 (g)  +  3 H2 (g) ΰ   2 NH3 (g)






























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Part D:  Derivation of Gibbs Free Energy Change & Discussion: 1 point


           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:


       Souniverse = ∆Sosystem + ∆Sosurroundings


Show this derivation with stepwise explanations/comments:



































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Part E:  Reaction Spontaneity Calculation:                1 point


           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)  ∆Ho = +98.8 kJ;

                                                                                           ∆So = +341.5 kJ/K


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












At what temperature will the reaction be become spontaneous?


























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Part F:  Calculation ∆Go from ∆Ho and  So                 1 point


  Using the quantity called the Standard Gibbs free-energy change (∆Go),   


  ∆Go = ∆Ho - T∆So,


  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 25oC?










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






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








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Part G:  Calculation of ∆Go Values from ∆Gof Values  1 point
































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Part H:  Calculation of an Equilibrium Constant  from ∆Go Values

                                                                                             1 point


  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 25oC.


          Additional Values from Appendix B:

             Gof CO  =   51.3 kJ/mol

          ∆Hof CO  =   -110.5 kJ/mol

             So CO  =    197.6 J/K∙mol                   

             So H2    =     130.6 J/K∙mol

          Gof CH3OH  =   -166.4  kJ/mol

          ∆Hof CH3OH= -201.2 kJ/mol

             So CH3OH= 238 J/K∙mol























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Part K: Chapter 16 Key Terms            1 point


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 25oC 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