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?

Question

H2O, HBr, HCN, H2S, C2H2

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 and I got 34.08 and this is the mm for H2S. Is this correct?

Answer 1

That looks ok to me.
H2O is about 18
HBr = about 80 or so
HCN is about 27
H2S is about 34
C2H2 is about 26.

Answer 2

Ok thank you

Answer 3

that is correct. The MM for Hs@ is 34.1. Closes to 5.02/0.147=34.15.

Answer 4

You can also use d=PM/RT. Density is mass/volume. Plug it in and solve for M.