Solving a Hydrocarbon Molar Mass Problem

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Discussion Overview

The discussion revolves around solving a problem related to the molar mass of a hydrocarbon based on its composition and density relative to air. Participants explore the relationships between the percentages of carbon and hydrogen, the implications of density, and the necessary equations to derive the molar mass.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Homework-related

Main Points Raised

  • One participant presents a hydrocarbon composition of 92.3% carbon and 7.7% hydrogen and seeks to establish equations to find the values of x and y in CxHy.
  • Another participant questions the units of density, suggesting it may be in g/dm³.
  • A different participant clarifies that the density ratio refers to the density of the hydrocarbon in gaseous form compared to air, and provides a method to calculate the molar mass of air to relate it to the hydrocarbon's molar mass.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the exact approach to solving the problem, as different interpretations of the density and its implications are presented.

Contextual Notes

The discussion includes assumptions about the density of air and the method for calculating the molar mass based on the given percentages, but these assumptions are not fully resolved or agreed upon.

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 :)
 
Last edited:

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