Review 18ANS

REVIEW QUESTIONS
Chapter 18

Calculate the heat of reaction ( ) in for the reaction shown below, given the values for each substance:

Given for the reaction shown below, calculate the for .

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)
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?

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?

A reaction has and . At what temperature is the change in entropy for the reaction equal to the change in entropy for the surroundings?

Determine the entropy change ( ) in for the reaction shown below, given the standard entropies for each:

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:

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.

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

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

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.

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

for this reaction if the reaction mixture consists of 1.0 atm of

, 3.0 atm of

and 1.0 atm of

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

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

Review 18ANS

REVIEW QUESTIONS Chapter 18

REVIEW QUESTIONS
Chapter 18