The temperature of an ideal monatomic gas is increased from 300 K to 500 K. What is the change in molar entropy of the gas (a) if the volume is held constant and (b) if the pressure is held constant?

Water is vaporized reversibly at 100 °C and 1.01325 bar. The heat of vaporization is
1
40.69 kJ mol .− (a) What is the value of S∆ for the water? (b) What is the value of S∆ for the
water plus the heat reservoir at 100 °C?
2. Assuming that CO2 is an ideal gas, calculate H∆ ° and S∆ ° for the following process:
2 21CO ( g, 298.15 K,1bar) 1CO ( g,1000 K,1bar)→
Given: 3 7 2
26.648 42.262 10 142.40 10PC T T° − −
= + × − × in 1 1
J K mol− −
3. The temperature of an ideal monatomic gas is increased from 300 K to 500 K. What is the change
in molar entropy of the gas (a) if the volume is held constant and (b) if the pressure is held constant?
4. Ammonia (considered to be an ideal gas) initially at 25 °C and 1 bar pressure is heated at constant
pressure until the volume has trebled. Calculate (a) q per mole, (b) w per mole, (c) ,H∆ (d) ,U∆
and (e) .S∆
Given: 3 7 2
25.895 32.999 10 30.46 10PC T T− −
= + × − × in 1 1
J K mol .− −
5. (a) A system consists of a mole of ideal gas that undergoes the following change in state
1X(g, 298 K,10 bar) 1X(g, 298 K,1bar)=
What is the value of S∆ if the expansion is reversible? What is the value of S∆ if the gas expands
into a larger container so that the final pressure is 1 bar? (b) The same change in state takes place,
but we now consider the gas plus the heat reservoir at 298 K to be our system. What is the value of
S∆ if the expansion is reversible? What is the value of S∆ if the gas expands into a larger
container so that the final pressure is 1 bar?
6. An ideal gas at 298 K expands isothermally from a pressure of 10 bar to 1 bar. What are the value
of w per mole, q per mole, , ,U H∆ ∆ and S∆ in the following cases? (a) The expansion is
reversible, (b) The expansion is free, (c) The gas and its surroundings form an isolated system, and
the expansion is reversible, (d) The gas and its surroundings for an isolated system, and the
expansion is free.
7. The purest acetic acid is often called glacial acetic acid because it is purified by fractional freezing
at its melting point of 16.6 °C. A flask containing several moles of liquid acetic acid at 16.6 °C is
lowered into an ice-water bath briefly. When it is removed it is found that exactly 1 mol of acetic
acid has frozen.
Given:
( ) 1
fus 3 2CH CO H 11.45 kJ molH −
∆ = and ( ) 1
fus 2H O 5.98 kJ l .moH −
∆ = (a) What is the change
in entropy of the acetic acid? (b) What is the change in entropy of the water bath? (c) Now consider

the water bath and acetic acid are in the same system. What is the entropy change for the combined
system? Is the process reversible or irreversible? Why