Asked by Anna

Helium gas, He, at 22 degrees C and 1.00 atm occupied a vessel whose volume was 2.54 L. What volume would this gas occupy if it were cooled to liquid-nitrogen temperature (-197 degrees celcius).

What is the equation?
Answered by Trig
Always start with PV/nT = PV/nT, where P is the pressure, V is the volume, n is the number of moles, and T is the temperature. Take out whichever terms you don't need. In this case, you don't need n (the number of moles), so you're left with:

PV/T = PV/T

Solve for the V on the right side of the equation after you plug in everything else.
Answered by Trig
( You only use PV=nRT when none of the variables change. In this case the temperature is changing, so you use PV/nT = PV/nT )
Answered by Anna
I did that and got -22.7.

1st of all the answer is supposed to be .65 L

2nd of all where does the negative go?
Answered by Trig
Temperature must always be in Kelvin! Add 273 to the temperature in Celsius to get the temperature in Kelvin. In this case:

INITIAL TEMPERATURE = 22+273 = 295 K
FINAL TEMPERATURE = -197+273 = 76 K
Answered by Anna
ooh ok that explains it lol thanks =]
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