REVIEW QUESTIONS
Chapter 18

  1. Calculate the heat of reaction ( ) in for the reaction shown below, given the values for each substance:
  1. Given for the reaction shown below, calculate the for .
  1. The air within a piston equipped with a cylinder absorbs 565 J of heat and expands from an initial volume of 0.10 L to a final volume of 0.85 L against a pressure of 1.0 atm . What is the change in the internal energy of the air within the piston?


    (work is done by the system)
  2. How much work (in J ) is required to expand the volume of a pump by 2.5 L against an external pressure of 1.1 atm ?
(negative sign indicates work is done by the system)
5. Calculate the work associated with the following reaction at 1.00 atm and . Is the work done by the system or on the system?
  1. The enthalpy change for vaporization of methanol at is . If the entropy of methanol vapor at is , what is the entropy of the liquid methanol at this temperature?
  1. A reaction has and . At what temperature is the change in entropy for the reaction equal to the change in entropy for the surroundings?
  1. Determine the entropy change ( ) in for the reaction shown below, given the standard entropies for each:
  1. Given the following thermodynamic data, estimate the temperature ( ) at which the reaction shown below becomes spontaneous.
Reaction reaches equilibrium when Therefore,
Temperature must be greater than for reaction to become spontaneous
10. Calculate the free energy ( ) in kJ for the reaction shown below, given the values for each substance:
  1. Methanol can be produced by the reaction shown below, with the following thermodynamic data given at .
-110.5 0 -238.6
-137.3 0 -166.2
+197.9 +126.8
a) Calculate and for this reaction
b) Calculate (in ) for this reaction.
c) Calculate for hydrogen.
  1. At the equilibrium constant, , for the reaction below is 0.281 atm .
a) What is for this reaction?
b) If requires 193 J to vaporize 1.00 g of liquid bromine at and 1.00 atm . Calculate and at for this reaction.
c) Calculate the normal boiling point of bromine. Assume and are not affected by temperature. (Hint: At the normal boiling point liquid and vapor are in equilibrium)
At normal boiling point
  1. can be prepared by the reaction shown below:
For , and
a) Calculate the value of the equilibrium constant for this reaction at .
b) Calculate for this reaction at .
c) If produced were a liquid instead of a gas, how would the for the reaction be different (sign and magnitude) than calculated above? Explain.
If produced was a liquid, would be a larger negative number, since liquid is more ordered than gas and has less entropy.
14. Production of ammonia from nitrogen and hydrogen gases is an important industrial reaction shown below:
a) Calculate for this reaction at . Assume and are not temperature dependent.
b) Calculate at for this reaction if the reaction mixture consists of 1.0 atm of , 3.0 atm of and 1.0 atm of .
  1. What are the signs of and for the sublimation of dry ice (solid ) at ?
Since sublimation of dry ice is endothermic, positive (+)
Since gas has greater entropy than solid, positive (+)
Since dry ice sublimes at spontaneously, negative (-)
16. Using the following data, calculate the value of for , one of the least soluble of the common nitrate salts.
Species
  1. Show that hydrogen cyanide (HCN) is a gas at by estimating its normal boiling point from the following data:
)
108.9 113
135.1 202
The normal boiling point of HCN is the temperature at which liquid and gaseous HCN are in equilibrium:
At equilibrium
Since is less than would exist as a gas at this temperature