Posted by
**Emily** on
.

A sample of gas occupies a volume of 59.9 mL. As it expands, it does 126.2 J of work on its surroundings at a constant pressure of 798 torr. What is the final volume of the gas?

a. 61.1 mL

b. 1,250 mL

c. 218 mL

d. 1,490 mL

e. None of the above

I used the work function w = -PΔV and I performed the following conversions:

-126.6 J = -1.2458 L*atm

798 torr = .9524 atm

I plugged these values in to the equation:

-1.2458 L*atm = (.9524 atm)(ΔV)

ΔV = 1.30806 L

I then added the original volume of 59.9 mL to this value to get around 1,367 mL for the final volume, but this is apparently incorrect. I found if I subtracted 59.9 mL from 1.30806 L I got the correct answer, but I didn't know if this was the proper way to reach the answer.

So long story short, is subtracting the value of the original volume from ΔV correct, and if so, why?