# How to read the PiVi^gamma = PfVf^gamma formula?

1. May 7, 2012

### daleklama

1. The problem statement, all variables and given/known data

An ideal monatomic gas is held initially at a pressure of 1 atmosphere in a volume of 10L. It is compressed to 4L in an adiabatic process.
There are 0.8 moles.
Find the final pressure of the gas.
gamma = 1.667

2. Relevant equations

PiVi^gamma = PfVf^gamma

3. The attempt at a solution

I pretty much know what I'm doing, except I'm not sure what the formula means! Does it mean (PiVi)^gamma, or (Pi).(Vi^gamma?)

I always assumed it was the second, but I'm doubting it now. I got a huge answer (10,190 x 10^5 Pascals) and I'm not sure if it's reasonable.

Thank you!

2. May 7, 2012

### HallsofIvy

Staff Emeritus
The way you wrote it, it is (pi)(Vi)^gamma.

Further, the Wikipedia article on "adiabatic processes", http://en.wikipedia.org/wiki/Adiabatic_process
says that an adiabatic process gives $PV^{\gamma}= Constant$ so the way you have written it is correct- it is only the volume that is raised to a power.

3. May 7, 2012

### daleklama

Okay, thank you very much! Thats what I thought it must be :) Great!