Molar Mass of Gas Calculator
Calculate molar mass, mass, or moles of gases using the ideal gas law (PV = nRT)
Calculate Gas Properties
Gas Conditions
Gas pressure (standard: 1 atm = 101.325 kPa)
Gas temperature (STP: 0°C = 273.15 K)
Gas volume (STP: 22.4 L/mol for ideal gas)
Gas Properties
Total mass of the gas sample
Calculation Summary
Pressure: 1.000 atm
Temperature: 298.1 K (25°C)
Volume: 1.000 L
Using: PV = nRT (R = 0.0821 L·atm/mol·K)
Calculation Results
Gas Analysis
Calculation Details
Ideal Gas Law: PV = nRT
Step-by-step calculation:
n = PV/RT = (1.000 atm × 1.000 L) / (0.0821 × 298.1 K) = 0.040853 mol M = mass/moles = 0.000 g / 0.040853 mol = 0.00 g/mol
Gas classification:
Gas Properties Analysis
Example Calculation
Finding Molar Mass of Unknown Gas
Question: A 2.5 g sample of an unknown gas occupies 1.2 L at 25°C and 1.1 atm. What is its molar mass?
Given: mass = 2.5 g, V = 1.2 L, T = 25°C = 298.15 K, P = 1.1 atm
Find: Molar mass (M)
Gas constant: R = 0.0821 L·atm/mol·K
Step-by-Step Solution
Step 1: Calculate moles using ideal gas law
n = PV/RT = (1.1 atm × 1.2 L) / (0.0821 × 298.15 K) = 0.0539 mol
Step 2: Calculate molar mass
M = mass/moles = 2.5 g / 0.0539 mol = 46.4 g/mol
Answer: The molar mass is 46.4 g/mol (likely NO₂ or similar compound)
Ideal Gas Law
PV = nRT
P = Pressure (atm, kPa, bar)
V = Volume (L, mL, m³)
n = Number of moles
R = Gas constant
T = Temperature (K)
Key equations:
• n = PV/RT (find moles)
• M = mass/moles (molar mass)
• mass = M × n (find mass)
Gas Constants
Standard Conditions
STP (Standard Temperature and Pressure)
Temperature: 0°C (273.15 K)
Pressure: 1 atm (101.325 kPa)
Molar volume: 22.4 L/mol
Room Conditions
Temperature: 25°C (298.15 K)
Pressure: 1 atm
Molar volume: ~24.5 L/mol
Common Gas Molar Masses
Understanding Gas Molar Mass Calculations
What is Molar Mass?
Molar mass is the mass of one mole of a substance, typically expressed in grams per mole (g/mol). For gases, we can calculate molar mass using the ideal gas law when we know the mass, pressure, volume, and temperature of a gas sample.
Why is this Important?
- •Identify unknown gases in analytical chemistry
- •Calculate gas densities and properties
- •Determine molecular formulas of gaseous compounds
- •Quality control in industrial gas production
Gas Law Applications
Ideal Gas Assumptions
Gas particles have no volume and no intermolecular forces
Best for high T, low P conditions
Real Gas Behavior
Deviations occur at high pressure or low temperature
Use van der Waals equation for precision
STP Calculations
One mole of gas = 22.4 L at STP
Standard reference for gas calculations