I still use ideal gas law right? but how do i begin this?

Question

Calculate the density of hydrogen sulfide gas, H2S, at 49 °C and 985. mmHg. Obtain the density in grams per liter?

Answer 1

Yup!

PV=nRT
D=m/V

(n)(MW)=m; MW is the molecular weight of a substance

n=m/MW

PV=(m/MW)RT
(P)(MW)=(m/V)RT
(P)(MW)=DRT
((P)(MW))/RT=D

where D is the density

MW = 34g/mol
convert first 985mmHg to atm using this convertion ratio 1atm:760mmHg
use 0.08206L-atm/mol-K as the R
convert temp to absolute temperature by adding 273.15 to 49degC

Answer 2

Atomic weights: H=1 S=32 H2S=34

49C = 322K

34gH2S/22.4LH2S x 273K/322K x 985mmHg/760mmHg = 1.67g/L

T = 322, which is higher than 273, so volume goes up. But volume increases in thedenominator, so multiply by 273/322 to make the whole fraction smaller.

P = 985, which is higher than 760, so volume goes down. But in decreases in the denominator, so etc.

Answer 3

You're missing a piece of information that you need to solve the problem. You have P and T, but you still need V or n in order to figure the rest out.