How Is the Molar Mass of Gas X Calculated?

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SUMMARY

The molar mass of gas X is calculated using the mass of the gas and its volume under specific conditions. In this discussion, the mass of gas X was determined to be 0.3334g from a 250cm³ flask, leading to an incorrect initial calculation of 1.3336g/dm³. The correct molar mass, when recalculated under room temperature and pressure (RTP) conditions, is 34g/mol, using the ideal gas law and the molar volume of 24.2 L/mol.

PREREQUISITES
  • Understanding of the ideal gas law
  • Knowledge of standard temperature and pressure (STP) and room temperature and pressure (RTP)
  • Basic skills in unit conversion (e.g., cm³ to dm³)
  • Familiarity with molar mass calculations
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  • Learn about the ideal gas law and its applications
  • Study the concept of molar volume at different temperatures and pressures
  • Explore the differences between STP and RTP conditions
  • Practice calculations involving gas densities and molar masses
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Chemistry students, educators, and professionals involved in gas calculations and molar mass determinations will benefit from this discussion.

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the mass of a 250cm3 round bottomed flask is filled with gas X is determined to be 16.2850g. the mass of the empty flask and stopper is 15.9516g. what is the molar mass of gas X?

am i right to do it this way:

mass of gas X alone = 16.2850 - 15.9516 = 0.3334g
volume of gas X = 250/1000 = 0.25 dm3

molar mass of gas X = 0.3334/0.25 = 1.3336g/dm3

however, the answer is 32g, where did i make a mistake?

thank you
 
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what conditions are you working under?? STP?

molar mass= g/mol
not g/L

If its at room temp then you have:
295K
1 atm
24.2 L/mol

.250L/(24.2L/mol)= .01033mol

.3334g/.01033mol= 34g/mol
 
Last edited:
working under rtp

thank you
 

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