Rate of Effusion Calculator
Estimate how quickly two gases effuse through a small orifice based on their molar masses.
Time required for gas A to effuse a fixed amount.
Rate ratio (gas A / gas B)
1.254
Time for gas B
47.863 s
How to Use This Calculator
Gather molar masses
Use molar masses in g/mol for each gas you wish to compare.
Measure or estimate effusion time
Provide the time for gas A to effuse a fixed amount through the same opening.
Review rate ratio
The output gives the rate of gas A relative to gas B based on Graham's law.
Adjust calculations as needed
Use the time for gas B to plan experiments or compare with observed data.
Formula
rA / rB = sqrt(MB / MA)
tB = tA / (rA / rB)
MA and MB are molar masses of gas A and B. r indicates effusion rate, t effusion time for a fixed amount of gas.
Example
For nitrogen (28 g/mol) and carbon dioxide (44 g/mol), rA/rB = sqrt(44/28) about 1.25. If nitrogen takes 60 s, CO2 takes 60 / 1.25 about 48 s.
Full Description
Graham's law relates effusion rates inversely to the square root of molar mass assuming ideal gases, equal temperatures, and dilute pressure conditions.
This tool helps chemists and engineers compare gases for leak detection, isotope separation, or vacuum system design.
Frequently Asked Questions
Does temperature matter?
The law assumes both gases are at the same temperature. If temperatures differ, additional corrections are needed.
Can I compare more than two gases?
Yes. Reuse the calculator with new combinations or compute rates relative to a common reference gas.
What if the opening is large?
Graham’s law applies to molecular effusion through small orifices. Larger openings may require viscous flow analysis.
Do I need molar mass or molecular weight?
Molar mass and molecular weight (in g/mol) are interchangeable terms for this calculation.
Are real gas effects important?
At high pressures or for polar gases, deviations may occur. Use measured rates to calibrate the model if precision matters.