Help How to get the mole fraction ?

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Discussion Overview

The discussion revolves around calculating the mole fraction of ethylene glycol in an aqueous antifreeze solution that is 37.0% by mass. Participants explore the mathematical approach to determine the mole fraction, considering the densities and molar masses involved.

Discussion Character

  • Homework-related, Mathematical reasoning

Main Points Raised

  • One participant presents a method for calculating the mole fraction using the formula X = nA/(nA+nB), where they define nA and nB based on the mass percentages and molar masses of ethylene glycol and water.
  • Another participant suggests that the initial mathematical approach is correct but indicates that the result obtained by the first participant is incorrect.
  • A third participant confirms the previous assertion about the correctness of the equation but also states that their own calculated result of 14.6% is incorrect.
  • A later reply mentions that the system does not accept percentage values, implying a potential misunderstanding in the format required for the answer.

Areas of Agreement / Disagreement

Participants generally agree that the mathematical approach is valid, but there is disagreement regarding the correctness of the calculated results. The discussion remains unresolved regarding the accurate mole fraction value.

Contextual Notes

There are limitations related to the assumptions made about the solvent and the interpretation of percentage values in the context of the calculation.

zhen
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An aqueous antifreeze solution is 37.0% ethylene glycol (C2H6O2) by mass. The density of the solution is 1.047 g/cm3.

Q: Calculate the mole fraction of ethylene glycol.

I tried it many time, but still got the wrong answer.

that is what i did:

mole fraction:(X) = nA/(nA+nB)
set the mass of the solution - m
molar mass of C2H6O2: 62
molar mass of H2O: 18 --- (I think the solvent should be H2O...but not quite sure)

=> [(0.37 * m)/62]/[(0.37 * m/62 + 0.63 * m/18)]
= 13.8%------but that is wrong

need help...please
 
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Check your math - equation is OK, just the result is wrong.
 
oh...never mind...
the system does not accept percentage...
 

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