Easy Gen Chem q... am overthinking it?

[mestrada9447]

Destroyer 2009 GC #116:

This is a ridiculously easy question but when I looked at the answer they got the same answer as me but using a totally different route....


A gas has a density of 1.52g/L at STP which gas is it?

a. Cl2
b. H2S
c. CH4
d. C3H8
e. B2H6


They used:
P(MW)=DRT
1*MW=1.52*.0821*273
MW= 34 g/mol


I used:

1mol gas=22.4L
therefore :

1.52g/L*22.4L/mol=34 g/mol



Am I wrong by doing it this way?.... or do they mean the same thing?
Does 22.4L=1mol only apply to gases and should i only use that when they specify that it is in gas state?

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[AlbinoPolarBear]

It works at STP, because at STP, 1 mol of gas = 22.4 L

PV = nRT
V = nRT/P

At STP:
n = 1 mol
R = 0.08206 atm*L/(mol*K)
T = 273 K
P = 1 atm

V = (1*0.08206*273)/1
V = 22.4 L

So you can jump steps if it says it's at STP.

 

[mestrada9447]

awesome. Thanks!