# Entropy and a baloon of gas

1. Nov 28, 2006

### Gemstone

Me and a friend has recently fallen into a dead-end with an assignment we have, because we can't calculate the total entropy of a baloon filled with Helium.

Basicly, the assignment goes:
We have a baloon with 10 mol of Helium, inside a house with a temperature of 25 degrees celcius (that is, 298 kelvin). Now, we take the baloon outside to a temperature of -5 degrees clecius (268 kelvin).

Now, we're supposed to calculate the total entropy of the baloon and the environment. Anyone willing to help us out?

We've this far deducted that the pressure is 101,3 KPa (1 atmosphere)... which is by far the longest we've come.

Any help is appreiciated

2. Nov 30, 2006

### Agnostic

Entropy is:

S=kLn(Ω)

Where Ω is the multiplicity of the system.

Also. ∆S=∫dQ/t

This should help get you started.

3. Nov 30, 2006

### Mute

I think starting from the statistical definition of entropy would be a bit much for this problem. =P I think the formulae for ideal gases are well known enough that they can just be used right from the start.

So, since you're dealing with helium, you can indeed treat the gas in the balloon as an ideal gas.