Question #4787

Exactly 500 cubic centimeters of a gas at 1 atmosphere and 0 degrees Celsius weighs 0.581 grams. The composition of the gas shows it to be composed of only carbon and hydrogen, the carbon being 92.24%. What is the molecular formula of this gas?

Expert's answer

The STP are mentioned -> we can use the law, that 1 mole of any gas has 22,4L

nu=V/V0

nu=0.5/22.4=0.02232 mol

M=m/nu

M=0.581/0.02232=26

omega=M(C)*x/(M(C)*x+M(H)*y)

0.9224=12x/(12x+y)

11.0688x+0.9224y=12x

0.9312x=0.9224y

x is approximately equal to y

When x=1 y=1 M=12+1=13 no

& x=2 y=2 M=12+12+1+1=26 YES!

& x=3 y=3 M= 12+12+12 +1+1+1=39 too much

Answer: C2H2

nu=V/V0

nu=0.5/22.4=0.02232 mol

M=m/nu

M=0.581/0.02232=26

omega=M(C)*x/(M(C)*x+M(H)*y)

0.9224=12x/(12x+y)

11.0688x+0.9224y=12x

0.9312x=0.9224y

x is approximately equal to y

When x=1 y=1 M=12+1=13 no

& x=2 y=2 M=12+12+1+1=26 YES!

& x=3 y=3 M= 12+12+12 +1+1+1=39 too much

Answer: C2H2

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