need chem help please!?

Question

What is the volume of 175 mL of oxygen gas at 91.5°C and 620. mm Hg if the conditions are adjusted to STP? Assume the amount of gas is held constant.

Answer 1

P1V1/T1 = P2V2/T2

(620mm)(175mL)/(324.5K) = (760)(V)/(273K)

V = (620)(175)273)/(324.5)(273)

Answer 2

Here are some hints:

(PV/nRT) under the conditions you listed will equal (PV/nRT) at STP. STP is 0 deg. C and 760 mm Hg.

The number of moles and the gas constant R don't change, so take n and R out of the equation...

PV/T before = PV/T at STP.
(620.)(175)/(91.5) = (760)(V)/(0)

You'll notice that the right side of this equation involves dividing by zero, which is not allowed, so convert the temperatures to Kelvins by adding 273.15.

(620.)(175)/(364.65) = (760)(V)/(273.15)
Solve for V.

Remember that higher pressures cause gases to compress and have smaller volumes (Boyle's Law). Same for lower temperatures (Charles's Law). Since STP is a higher pressure and lower temperature than the original conditions, your answer should be a smaller volume than 175 mL.