How do you find the molecular mass and formula using gas densities?

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SUMMARY

This discussion focuses on calculating molecular mass and formulas using gas densities, specifically through the Ideal Gas Law (PV=nRT). At standard temperature and pressure (STP), one mole of gas occupies 22.4 liters, allowing for the conversion of gas density (grams per liter) into grams per mole, which yields the Gram Molecular Weight. Participants emphasize the importance of recalculating gas density to STP conditions when provided with data at different temperatures and pressures to ensure accurate molecular mass calculations.

PREREQUISITES
  • Understanding of the Ideal Gas Law (PV=nRT)
  • Knowledge of standard temperature and pressure (STP) conditions
  • Familiarity with gas density calculations (grams per liter)
  • Basic concepts of molecular weight and molar mass
NEXT STEPS
  • Study the Ideal Gas Law applications in various conditions
  • Learn how to convert gas densities from different temperatures and pressures to STP
  • Explore methods for calculating molecular weight from empirical formulas
  • Investigate the relationship between gas density and molecular structure
USEFUL FOR

Chemistry students, educators, and professionals involved in gas analysis and molecular calculations will benefit from this discussion.

Hunus
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How does one use ratios of gas densities to estimate the molecular mass and find the molecular
formulas?
 
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Conceptually keep in mind Ideal Gas Law PV=nRT can allow one to show that at STP one mole of gas molecules exist in 22.4 liters of volume.
since gas density is gms/ liter (mass/volume) one can calculate the gms of gas from the density to make 22.4 liters or one mole of gas... gms per mole then gives a Gram Molecular Weight

If the density is given at a different temperature and pressure recalculate it for STP
 
MrSid said:
Conceptually keep in mind Ideal Gas Law PV=nRT can allow one to show that at STP one mole of gas molecules exist in 22.4 liters of volume.
since gas density is gms/ liter (mass/volume) one can calculate the gms of gas from the density to make 22.4 liters or one mole of gas... gms per mole then gives a Gram Molecular Weight

You are right, but mixing mass and "grams of gas" in one sentence is not a good idea. "Grams" are not a synonym of "mass".

If the density is given at a different temperature and pressure recalculate it for STP

No need for that - you can calculate volume of 1 mole of gas for these conditions and use this volume to calculate mass of 1 mole.
 

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