Rate of Diffusion Calculator
Calculate diffusion rates and compare gases using Graham's Law
How to Calculate Rate of Diffusion Formula?
The rate of diffusion refers to how quickly a gas spreads through a medium or how fast it escapes through a tiny hole (effusion). The primary formula used to calculate and compare these rates in chemistry and physics is Graham's Law of Diffusion.
This calculator uses Graham's Law to determine the relative speed of gas molecules based on their molar masses. Lighter gases diffuse faster than heavier gases.
Graham's Law Formula
The formula states that the rate of diffusion (or effusion) of a gas is inversely proportional to the square root of its molar mass. When comparing two gases, the formula is:
Where:
- Rate₁ = Rate of diffusion for Gas 1
- Rate₂ = Rate of diffusion for Gas 2
- M₁ = Molar Mass of Gas 1 (g/mol)
- M₂ = Molar Mass of Gas 2 (g/mol)
Real-World Example
Consider calculating the rate of diffusion for Helium (He) compared to Methane (CH₄).
- Identify Molar Masses:
- Mass of Helium (Gas A) ≈ 4.00 g/mol
- Mass of Methane (Gas B) ≈ 16.04 g/mol
- Apply the Formula:
Ratio = √(16.04 / 4.00) ≈ √4.01 ≈ 2.002 - Result: Helium diffuses approximately 2 times faster than Methane because it is significantly lighter.
Factors Affecting Rate of Diffusion
While molar mass is the primary factor in Graham's Law, other factors influence diffusion in real-world scenarios:
- Temperature: Higher temperatures increase the kinetic energy of particles, leading to faster diffusion rates.
- Concentration Gradient: Gases move from areas of high concentration to low concentration. A steeper gradient increases the rate (described by Fick's Law).
- Medium: Diffusion is faster in a vacuum or gas than in a liquid or solid.
Frequently Asked Questions
What units should I use for the rate?
Graham's Law deals with ratios, so the units for rate do not strictly matter as long as they are consistent (e.g., both in m/s, mL/min, or mol/hr). Our calculator preserves whichever unit you input.
Does this apply to liquids?
Graham's Law is specifically an approximation for gases. Diffusion in liquids is much slower and depends heavily on viscosity and particle size, usually modeled by the Stokes-Einstein equation.