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Thermodynamics

Quiz Number:  6
Course Name:  Chemistry
Course No.132
Quiz N0. : 6
Teacher:  Billy Cook
Teacher's Home Page:  http://www.iaonline.com/chemistry/chemistr1.htm
Teacher's Email:  Bcook@icc.cc.il.us









No. of Questions=  5


























    1. 

The Gibbs Free Energy is given by the equation:
        
    
        



    

    















    

    
    
        a)
        
    DG = DS  -  TDH.
        
    




    

    
    
        b)
        
    DG = Ginitial - Gfinal
        
    




    

    
    
        c)
        
    DG = DH - TDS
        
    




    

    
    
        d)
        
    DG = DS - HDT
        
    




    

    
    
        e)
        
    DG = DH - SDT
        
    




    
    

    
    







    
    
        


        










    
    
        


        








    2. 

Consider the following reaction carefully and determine the sign of DSo
for the reaction it describes.


NH4Cl(s)  aro.jpg (800 bytes)  NH3(g)  +  HCl(g)
              DH = +176 kJ



Which of the following statements describes the thermodynamic spontaneity of the
reaction?
        1. The reaction is spontaneous at all
temperatures.



        2. The reaction is spontaneous only at
relatively high temperatures.



        3. The reaction is spontaneous only at
relatively low temperatures.


        		
    
        



    

    















    

    
    
        a)
        
    1 only
        
    




    

    
    
        b)
        
    2 only
        
    




    

    
    
        c)
        
    3 only
        
    




    

    
    
        d)
        
    1 and 2 only
        
    




    

    
    
        e)
        
    1, 2, and 3
        
    




    
    

    
    







    
    
        


        










    
    
        


        








    3. 

For the reaction


2 SO2(g)  +  O2(g)aro.jpg (800 bytes)2 SO3(g)



at 1 atm pressure, the values of DH and DS
are both negative, and the process is spontaneous at room temperature. Which of the
following statements is also true?
        

    
        



    

    















    

    
    
        a)
        
    DG is positive for the reaction at room temperature.
        
    




    

    
    
        b)
        
    DG is temperature independent.
        
    




    

    
    
        c)
        
    The change in entropy is the driving force of the reaction.
        
    




    

    
    
        d)
        
    At high temperatures, DH becomes positive.
        
    




    

    
    
        e)
        
    The direction of the reaction may be reversed at high temperatures.
        
    




    
    

    
    







    
    
        


        








    4. 

What is the minimum temperature required for the spontaneous conversion of CCl4(l)
to CCl4(g)  when DHo is 573 kJ/mol
and DSo is 1.64 kJ/mol.K
?
        
    
        



    

    















    

    
    
        a)
        
    76oC
        
    




    

    
    
        b)
        
    89oC
        
    




    

    
    
        c)
        
    189oC
        
    




    

    
    
        d)
        
    215oC
        
    




    

    
    
        e)
        
    349oC
        
    




    
    

    
    







    
    
        


        








    5. 

For the reaction


3 C(s)  +  4 H2(g) dblaro.jpg (896 bytes) C3H8(g)



DSo = -269 J/mol.K
  and DHo = +103.8 kJ/mol.  Calculate the
equilibrium constant at 25oC for the reaction.
        

    
        



    

    















    

    
    
        a)
        
    1.0
        
    




    

    
    
        b)
        
    5.5 x 10-33
        
    




    

    
    
        c)
        
    1.0 x 10-17
        
    




    

    
    
        d)
        
    3.7 x 1019
        
    




    

    
    
        e)
        
    2.1 x 10-32
        
    




    
    

    
    







    
    
        


        










    
    
        


        



















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