Chemistry

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Molar Mass of Gas Calculator.

Calculate gas molar mass from ideal-gas measurements and sample mass.

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Moles: 0.08923 mol

Moles

0.089230mol
Molar mass: 44.827939 g/mol

Molar mass

44.827939g/mol

Educational arithmetic only. Keep units consistent and use measured or explicitly supplied chemistry inputs; this tool does not infer reaction pathways, property tables, or safety guidance.

Use Cases

Determine molar mass of an unknown gas

Use experimental measurements of mass, pressure, volume, and temperature to find the molar mass, helping identify the gas.

Example: A 2.0 g gas sample at 101.3 kPa, 22.4 L, and 273 K has a molar mass of 2.0 g/mol.

Verify theoretical molar mass in lab

Compare calculated molar mass from lab data with known values to check purity or experimental accuracy.

Example: If a gas is expected to be CO2 (44 g/mol), measure and calculate to see if the result matches.

Frequently Asked Questions

How is the molar mass of a gas calculated using this calculator?
The calculator uses the ideal gas law (PV = nRT) to find the number of moles (n) from pressure, volume, and temperature. Then it divides the sample mass by the moles to get molar mass (g/mol).
What units are required for the inputs?
Sample mass must be in grams (g), pressure in kilopascals (kPa), volume in liters (L), and temperature in kelvin (K). Ensure all inputs are in these units for accurate results.
Can I use this calculator for real gases?
This calculator assumes ideal gas behavior, which is accurate at low pressures and high temperatures. For real gases under extreme conditions, results may deviate.

Tips & Common Mistakes

Tips

  • Ensure temperature is in kelvin (K). Convert from Celsius by adding 273.15.
  • Use consistent units: grams, kPa, liters, and kelvin. Convert if necessary.
  • For best accuracy, use measurements at low pressure and high temperature to approximate ideal gas behavior.
  • Double-check your inputs for typos, especially decimal points, to avoid calculation errors.

Common Mistakes to Avoid

  • Forgetting to convert temperature to kelvin, leading to incorrect moles and molar mass.
  • Using pressure in atm or mmHg without converting to kPa, causing errors in the calculation.
  • Mixing up volume units (e.g., mL instead of L) without conversion, skewing results.

Last updated: August 13, 2026