Exactly 5.02 grams of an unknown gas was sealed in a 3.0L flask at 37 degrees celsius and a pressure of 1.25 atm. Which on of the following is most likely to be the unknown?

I am not sure how to start this.

2 answers

Use PV = nRT and solve for n.
Then n = grams/molar mass. Solve for molar mass.
Compare with molar masses of the gases listed in the answer choices.
ok so I did (1.25)(3.0) = n(0.0821)(310)

3.75 = n(25.451)

n=0.1473

Then I did 0.1473= 5.02/mm but I am not sure if this is right.