# Homework Help: Ideal Gas Law Problem

1. Apr 22, 2014

### Bgerst103

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

A cylinder fitted with a movable piston contains ideal gas at 27C, pressure .5 x 10^5 Pa, and volume 1.25 m^3. What will be the final temperature if the gas is compressed to .8 m^3 and the pressure rises to .82 x 10^5 Pa.

A) 125 C
B) 154 C
C) 246 C
D) 67.7 C
E) 41.8 C

2. Relevant equations

P1V1/T1=P2V2/T2

3. The attempt at a solution

I thought this problem was going to be pretty simple. (.5 x 10^5 Pa x 1.25 m^3)/27 = (.82 x 10^5 Pa x .8 m^3)/T2. I keep getting T2 is equal to 28.3392. Is there something I'm missing? It seems like the pressure/volume ratio doesn't change that drastically so the temperatures would be close but the closest answer is at ~15 C increase. Any help is appreciated.

2. Apr 22, 2014

### Staff: Mentor

You have to use absolute temperatures.

Chet

3. Apr 22, 2014

### Bgerst103

Got it. I thought since it was ratios the units wouldn't affect the final outcome but I was wrong.

4. Apr 22, 2014

### dauto

Only when you're talking about temperature DIFFERENCES - not ratios - you may replace Kelvins with Celsius.