š¬ļø Molar Mass of Gas Calculator
Combine mass, pressure, volume, and temperature measurements to estimate the molar mass of a gaseous sample.
Mass of gas collected in the container.
Volume of the container or measured gas volume.
Convert Ā°C to K automatically by adding 273.15.
Molar Mass
14.5627 g/mol
Calculated via M = (mRT)/(PV).
Moles of Gas
0.1717 mol
From PV/(RT).
Density
0.7143 kg/mĀ³
Useful for comparing to known gas densities.
With temperature 298.15 K, the measured sample corresponds to 14.5627 g/mol. Compare this value against reference molar masses to identify the gas.
How to Use This Calculator
Collect measurements
Record mass (g), absolute pressure, container volume, and gas temperature. Correct for atmospheric pressure if needed.
Enter values with correct units
Select appropriate units for pressure, volume, and temperature. The calculator handles the conversions to SI units internally.
Review the calculated molar mass
The result shows molar mass, total moles, and an implied gas density. Use these to identify the gas or validate instrumentation.
Compare with reference data
Match the computed molar mass to known gases. Account for experimental uncertainty and deviations from ideal gas behaviour if necessary.
Formula
PV = nRT
M = m / n = (mRT) / (PV)
M is molar mass (g/mol), m is mass of gas (g), P is absolute pressure (Pa), V is volume (mĀ³), R is the gas constant (8.314 JĀ·mol^-1Ā·K^-1), and T is temperature (K).
Example
2.10 g of gas occupies 1.85 L at 97.8 kPa and 298 K. M = (2.10 g * 8.314 * 298) / (97.8 x 10^3 Pa * 1.85 x 10^-3 mĀ³) = 44.0 g/mol (approx. COā).
Full Description
Identifying gases often involves measuring how much mass occupies a known volume under controlled temperature and pressure. The ideal gas law links those measurements to the amount of substance, allowing you to compute molar mass for unknown gases or check the purity of a sample.
This calculator performs the conversions required to use SI units in the gas law, handles temperature conversions, and reports auxiliary values such as gas density. While most gases behave nearly ideally at moderate pressures and temperatures, deviations can occur; consider applying a compressibility factor (Z) for high-precision work.
Use the tool in analytical chemistry labs, environmental monitoring, or classroom demonstrations to reinforce the relationship between mass, moles, and state variables.
Frequently Asked Questions
Should I use gauge or absolute pressure?
Use absolute pressure in the calculation. Convert gauge readings by adding atmospheric pressure (~101.3 kPa at sea level).
Can I account for non-ideal behaviour?
For better accuracy, include a compressibility factor (Z) so that PV = ZnRT. Divide the final molar mass by Z if your gas deviates from ideality.
What unit is the density output?
Density is reported in kilograms per cubic meter (kg/mĀ³), which is convenient for comparison with published gas densities.
How sensitive is the result to measurement error?
Molar mass depends linearly on mass and temperature, and inversely on pressure and volume. Use calibrated instruments to reduce uncertainty.
Does humidity or water vapour matter?
If water vapour is present, correct the pressure for vapour pressure or dry the gas sample. Otherwise the molar mass will be biased low.