Avogadro's Law Calculator
Enter the initial volume, initial amount of substance, and final amount of substance to compute the final gas volume at constant temperature and pressure via V₁/n₁ = V₂/n₂.
Input Data
Results
At a glance:Enter the initial volume, initial amount of substance, and final amount of substance to compute the final gas volume at constant temperature and pressure via V₁/n₁ = V₂/n₂.
Formula
V₂ = V₁ × n₂ / n₁. (equivalently V₁/n₁ = V₂/n₂)
$$\dfrac{V_1}{n_1} = \dfrac{V_2}{n_2} \;\Rightarrow\; V_2 = \dfrac{V_1 n_2}{n_1}$$How to Use
- Enter the initial volume V₁ and initial amount n₁ (mol).
- Enter the final amount n₂ (mol).
- The calculator returns the final volume V₂.
FAQ
Is Avogadro's law the same as Avogadro's constant?
No. Avogadro's law is a gas law: at the same T and P, volume is proportional to moles (V∝n). Avogadro's constant is Nₐ ≈ 6.022×10²³, the number of particles in one mole. They are related but different concepts, both named after Avogadro.
Why does 1 mol of gas occupy 22.4 L at STP?
This is a consequence of Avogadro's law combined with the ideal gas law PV=nRT: plugging in standard conditions (0°C, 1 atm), n=1 mol, R, and T=273.15 K gives V≈22.4 L. It is called the standard molar volume and is approximately the same for all ideal gases.
Do different gases at equal volume really contain the same number of molecules?
Under the same T and P with the ideal-gas approximation, yes. This is the first statement of Avogadro's law and the reason gas reactions can use volume ratios to represent mole ratios. Real gases deviate slightly under extreme conditions.
Can I still use this formula if temperature or pressure changes?
No. Avogadro's law requires constant temperature and pressure. If T or P also change, use the combined gas law P₁V₁/T₁ = P₂V₂/T₂, or the ideal gas state equation PV=nRT, to handle all variables together.
Must volume be in litres?
L, mL, or m³ are all fine, as long as both sides of the equation use the same unit, because the formula is a ratio and units cancel. This calculator defaults to litres for easy comparison with the 22.4 L standard molar volume.
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References
Content review: Calculatorism Science Team. Results are for reference only; please refer to the relevant authorities for the official figures.