[cseil]

Hello everyone,
I have a problem with a pchem exercise.

There's a container kept at constant temperature (100°C) by a thermostat that transfers Q=11k cal.
Inside it there's another little container with H2O(l): it breaks up, water becomes vapour and expands into the main container.

The final pressure is 0.3atm.

I have to calculate W, ΔU, ΔH, ΔS, ΔG.

First of all, the system is the container. It has constant volume, so work is always 0.
ΔU is Q, Q is furnished by the thermostat. So ΔU = 11000cal.

ΔH is the sum of two processes:
1) H2O(l) becomes H2O(g)
2) H2O(g) 1atm -> H2O(g) 0.3atm

ΔH1 = ΔH_vap = 11740cal
ΔH2 = 0 because temperature is constant into the container and enthalpy changes only with temperature.

ΔH = ΔHvap

ΔS is the sum of ΔS1 and ΔS2.
ΔS1 is ΔH_vap/T = 34.47 cal/K
ΔS2 is -Rln(P2/P1) = 2.39 cal/K

ΔG can be calculated very easily with the expression ΔH - TΔS.

Is it right till here?

Now I have to do the same exercise but with N₂ into the container.
What do I do?

Thanks for your help