How to Calculate the Molar Mass of an Unknown Gas?

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SUMMARY

The discussion focuses on calculating the molar mass of an unknown gas using the ideal gas law. The provided data includes a mass of 0.810 g, pressure of 0.954 atm (converted to 96.66405 kPa), volume of 0.461 L, and temperature of 291 K. The ideal gas law equation PV=nRT is utilized to find the number of moles (n), which is then used to derive the molar mass (M) using the formula M=n*m. The calculated molar mass is approximately 44.0 g/mol.

PREREQUISITES
  • Understanding of the ideal gas law (PV=nRT)
  • Knowledge of unit conversions (atm to kPa)
  • Familiarity with the universal gas constant (R=8.314 J/(mol·K))
  • Basic algebra for manipulating equations
NEXT STEPS
  • Study the derivation and applications of the ideal gas law
  • Learn about unit conversions in gas calculations
  • Explore the significance of the universal gas constant in different contexts
  • Investigate real gas behavior and deviations from ideal gas law
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Chemistry students, educators, and professionals involved in gas calculations and thermodynamics will benefit from this discussion.

momen1981
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Given the following data for a gas, use the equation for the ideal gas law to calculate the molar mass.

Mass = 0.810 g
Pressure = 0.954 atm
Volume = 0.461 L
Temp = 291 K


M = mRT/PV = 44.0?
 
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I won't give you the answer but the following is how you solve the equation

PV=nRT

P=pressure (0.954 atm [use kpa since that is what is required in the ideal gas law thus pressure is 0.954*101.325 kpa = 96.66405 kpa])

V=volume (0.461 L)

R=Universal gas constant or 8.314

T=temperature (291 K)

m=mass (0.810 g)

n=mol (unknown)

M=molar mass (unknown)

PV=nRT which becomes

n=PV/RT

After you get mols, use this formula n=m/M or M=n*m
 
OK I understand now -- thank you!
 

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