Dr. Herrick's CH223
Pressure Quiz 6

     

 
      

2nd Law Thermodynamics
Copyright  D. Herrick
 

20 Questions from past exams.
Practice for speed.  Aim for 2 minutes per problem.

 

  

1. Thermodynamics says the maximum work by a system occurs
A) during a spontaneous process at constant pressure.
B) at constant temperature.
C) at constant volume.
D) when there is a catalyst present.
E) along a reversible pathway.

     

2. So for the reaction

2 H2O(g)    O2(g) + 2 H2(g)

is expected to be:
A) positive B) zero  C) negative  

   

3. Calculate Go (kJ) for the reaction at 25C

N2O(g)    N2(g) + 0.5 O2(g) ,
  Ho =  - 81.6 kJ
  So = + 75 J/K
A) -84 B) -104  C) -59   D) -80  E) -1957 

    

4. So for the reaction

C2H2(g) + 2.5 O2(g)  2 CO2(g) +  H2O(g)

is expected to be:
A) positive   B) zero  C) negative  

    

              

5. The total entropy of a system and its surroundings always increases in a spontaneous process.  This is a statement of:
A) the first law of thermodynamics.
B) the law of conservation of matter.
C) the second law of thermodynamics.
D) the third law of thermodynamics.
E) the law of constant composition.

     

6. A reaction R P has Ho = - 60 kJ and So = -100 J/K. The spontaneous reaction favors:
A) products at all temperatures.
B) reactants at all temperatures.
C) products at high temperatures, reactants at low temperatures.
D) products at low temperatures, reactants at high temperatures.

    

7. Determine Go (kJ) for the reaction at 25C:

H2(g) + Cl2(g)  2 HCl(g) , 
   KP = 2.57 × 1033
A) 191 B) 95   C) zero  D) -95  E) -191 

 

8. Calculate Go (kJ) for the reaction at 25C

Al(s) + Fe2O3(s)  2 Fe(s) + Al2O3(s), 
  Ho = - 484 kJ
  So = - 39 J/K
A) -503 B) -496   C) -472   D) -248  E) 5569

    

9. Determine Go (kJ) for the reaction at 25C:

AgCl(s)  Ag+(aq)  +  Cl-(aq), 
   K = 1.80 ×10-10
A) 4.66 B) 55.6   C) 24.1  D) -55.6  E) -24.1 

    

10. Thermodynamics says the heat absorbed by a chemical reaction at constant T and P is:
A) zero
B) the work done by the system along a reversible pathway
C) the enthalpy change for the system
D) the entropy change for the system
E) the free-energy change for the system

     

11. Thermodynamics says a spontaneous chemical reaction at constant T and P always has:
A) a negative change in the enthalpy of the system.
B) a negative change in the entropy of the system.
C) a negative change in the internal energy of the system.
D) a positive change in the entropy of the system.
E) a negative change in the free-energy of the system.

 

12. S for the reaction 

2 CH3OH(g) + 3 O2(g)  2 CO2(g) + 4 H2O(g)

is expected to be:
A) positive B) zero  C) negative  

     

13. S for the reaction

2 CH3OH(g) + 3 O2(g)  2 CO2(g) + 4 H2O(l )

is expected to be:
A) positive B) zero  C) negative  

     

14. The reactants and products in a chemical reaction at constant T and P are in a state of equilibrium whenever the:
A) enthalpy change from reactants to products satisfies H = 0
B) entropy change from reactants to products satisfies S = 0
C) free-energy change from reactants to products satisfies G = 0
D) reaction has H = 0 and S > 0
E) reaction has H = 0 and S < 0

     

15. A reaction R P has Ho = 104 kJ and So = 88 J/K when reactants and products are in their standard states.  At what temperature will Go = 0 ?
A) Go cannot be zero for this reaction.
B)  909C
C) -272C
D)  884C
E)  25C

 

16. According to the reaction data

CaCO3(s)  Ca 2+ (aq)  +  CO32– (aq) ,
  Ho = -12.4 kJ ,
   So = -201 J/K

the solubility of calcium carbonate in water between 0C and 100C should be:
A) weak in cold water; weaker in hot water.
B) strong in cold water; strong in hot water.
C) weaker in cold water; weak in hot water.
D) strong in cold water; weak in hot water.
E) weak in cold water; strong in hot water.
F) completely insoluble at all temperatures.

     

Questions 17-20 involve the reaction

CaCO3(s)    CaO(s)  +  CO2 (g) ,
  Ho = 178.3 kJ ,
  So = 159.0 J/K

which has a thermodynamic equilibrium constant K = Kp.

  

17. The equilibrium pressure (atm) of CO2 at 25C is:
A) 0.054 D) 2.17
B) 1.1 × 10-23 E) 1.8 × 10-4
C) 9.75 F) 18.2

     

18. The equilibrium pressure (atm) of CO2 at 500C is:
A) 0.054 D) 2.17
B) 1.1 × 10-23 E) 1.8 × 10-4
C) 9.75 F) 18.2

  

19. The equilibrium pressure (atm) of CO2 at 1000C is:
A) 0.054 D) 2.17
B) 1.1 × 10-23 E) 1.8 × 10-4
C) 9.75 F) 18.2

     

20. The temperature (C) at which the equilibrium pressure of CO2 is 1.00 atm is:
A) -21 B) 159  C) 848  D) 1273   E) 467  

  

 


 

 

   Copyright  D. Herrick