Solving a Hydrocarbon Molar Mass Problem

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The hydrocarbon problem involves determining the molar mass of a compound with 92.3% carbon and 7.7% hydrogen, given a smoke density ratio of 2.69 compared to air. The initial calculations suggest a ratio of carbon to hydrogen, leading to a formulation of equations to solve for the variables x and y. The density of the hydrocarbon's smoke is interpreted as a ratio of its molar mass to that of air, which is approximately 29 g/mol. By applying this density ratio, the molar mass of the hydrocarbon can be calculated as 2.69 times that of air. The discussion concludes with a confirmation of understanding the relationship between the densities and molar masses involved.
mohlam12
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Hey everyone,
I have this problem to solve:

A hydrocarbon (CxHy) contains 92.3% of Carbon and 7.7% of Hydrogen.
1) What is its molar mass, if the density of its smoke to the air is d=2.69 ?

92.3/7.7 = 12
So 12x=y
This is the first equation. I have to find a second one to find what is x and what is y, in order to find the molar mass of CxHy.

Is the density of water to the air can be written as d=(molar mass of the compound)/(molar mass of the water) ?

Anyhelp/hints would be appreciated.
Mohammed
 
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mohlam12 said:
1) What is its molar mass, if the density of its smoke to the air is d=2.69 ?

Which are the units of this density, g/dm^3 ?
 
Sounds like it is ratio of its density (in gaseous form) to the air density.

"Molar mass" of the air is about 0.78*28+0.21*32+0.01*40 (ie air has density as if it was gas of this molar mass). Hydrocarbon molar mass is 2.69 times higher.
 
Got It! Thanks Everyone :)
 
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