[Tachyon]

[kms137]

Webassign? Hate it! Haha anyway...

So you have a given volume, but this is the volume the He(g) expands to, so it is the final volume. Start by finding the initial volume. Take the moles, temperature, and pressure given and calculate a volume using the ideal gas law. This will give you your initial volume.

You now have a final and an initial volume, so you can use the equation dS=nRln(Vfinal/Vinitial)
This should give you an answer for dS (which is the change in entropy) in J/K. Don't forget, the R used in this step is 8.314 J/Kmol, which is different from the R used for the ideal gas law (0.08206).

Now, you need to go back and multiply your old S, which is given to you as 126.11 J/Kmol, by your amount of moles, so that will give you just J/K. Add this number to the dS you calculated and you should have your answer! This works for both parts, same process. Good luck!