Molar Mass of Gas Calculator

This calculator relies on two primary equations rooted in the Ideal Gas Law. First, the number of moles (n) of the gas is derived using the rearranged Ideal Gas Law equation: n = (P * V) / (R * T), where P represents absolute pressure, V is volume, R is the ideal gas constant, and T is absolute temperature in Kelvin. Once the number of moles is known, the molar mass (M) is calculated by dividing the sample mass (m) by the number of moles: M = m / n. The resulting value is expressed in grams per mole (g/mol).

Imagine you have a 2.50 gram sample of an unknown gas confined in a 1.20 liter container at a pressure of 1.05 atmospheres and a temperature of 298 Kelvin. Using the ideal gas constant R = 0.0821 L·atm/(mol·K), we first find the moles of gas: n = (1.05 * 1.20) / (0.0821 * 298) = 1.26 / 24.4658 ≈ 0.0515 moles. Next, we divide the mass by this mole value to find the molar mass: M = 2.50 g / 0.0515 mol ≈ 48.54 g/mol. This reveals the molecular weight of your gas sample.

Always ensure your units are consistent before entering data into the calculator. Temperature must always be converted to Kelvin by adding 273.15 to Celsius measurements. Additionally, verify that pressure and volume units match your chosen gas constant to avoid magnitude errors in your final molar mass result.