Calculate 1. !S (for the system) when the state of 2.50 mol of nitrogen gas is
changed from 25 oC and 2.00 atm to 125 oC and 8.00 atm. How do you
rationalizes the sign of !S? Assume that the nitrogen gas is an ideal gas.
2. The enthalpy of vaporization of ethanol is 43.5 kJmol-1 at its normal boiling point
of 352 K. Calculate (a) the entropy of vaporization of ethanol at this temperature
and, (b) the entropy of change of the surroundings.
3. (a) Calculate the Carnot efficiency of a primitive steam engine operating on steam
at 180 oC (hint: it is the hot reservoir) and discharging at 100 oC. (b) Repeat the
calculation for a modern steam turbine that operates with at steam 360 oC and
discharges at 100 oC.
4. Suppose that 2.5 mol Ar (g) occupies 72 dm3 at 298 K expands to 100 dm3.
Calculate !G for the process.
5. The change in the Gibbs energy of a certain constant pressure process was found
"G
to fit the expression
= -85.40 + 42.8 (T/K). Calculate the value of !S for the
T
*
# "G &
process. ,h int : % ( = )S /
$ "T ' p
+
.
!
6. Estimate the change in the Gibbs energy of 1.00 dm3 of ethanol when the pressure
acting on it us increased from 101.3 kPa to 202.6 kPa.
!
7. Calculate the change in the molar Gibbs energy of methane when its pressure is
increased isothermally from 101.3 kPa to 202.6 kPa at 500K.