Avogadro's Law Calculator

Apply Avogadro's Law: V is proportional to n (moles) at constant T and P. Find volume at different moles, or moles from volume ratios for any ideal gas at fixed conditions.

💨 Gas Laws📐 V1/n1 = V2/n2🧪 Chemistry

Initial volume V1 (L)

Initial moles n1

Final moles n2

OR Final volume V2 (find n2)

Please enter valid values.

Formula & Reference

Variable	Symbol	Formula	Units
Avogadro's Law Calculator	—	V1/n1 = V2/n2	L

Step-by-Step Examples

Example 1

Adding Gas

2.00 L gas at 0.100 mol. Add gas to reach 0.200 mol at same T,P.

V2 = V1*n2/n1 = 2.00*0.200/0.100
V2 = 4.00 L (doubled when moles doubled)

✓ V2 = 4.00 L

Example 2

Balloon Example

Balloon has 0.500 mol He at 12.0 L. Inflate to 18.0 L. Moles now?

n2 = n1*V2/V1 = 0.500*18.0/12.0
n2 = 0.750 mol (25% more gas)

✓ n2 = 0.750 mol

Example 3

Mole Ratio from Volume

Equal volumes of gas at same T,P contain equal moles.

1 L N2 at STP = 1/22.4 mol = 0.0446 mol
1 L CO2 at STP = 0.0446 mol (same)
Volume ratio = mole ratio for ideal gases

✓ Equal volumes contain equal moles at same T, P

Real-World Applications

⚗️

Gas Stoichiometry

Volume ratios in balanced equations equal mole ratios for gases at same T,P.

💨

Industrial Gas

Gas delivery measured by volume. Moles calculated from volume and conditions.

🧪

Avogadro Hypothesis

Foundation of gas stoichiometry: equal volumes of gases at same conditions contain equal numbers of molecules.

🚢

Respiratory Physiology

Lung volume and moles of air breathed. Tidal volume (~500 mL) contains ~0.022 mol air at body conditions.

Common Mistakes to Avoid

⚠️

T and P must be constant

Avogadro Law: V/n = constant only at fixed temperature and pressure. If T or P changes: use ideal gas law.

⚠️

Volume ratio equals mole ratio

At same T,P: V1/V2 = n1/n2. In balanced gas reactions: volumes react and produce in simple ratios.

⚠️

Standard molar volume

At STP (0 C, 1 atm): 1 mol ideal gas = 22.4 L. At SATP (25 C, 1 bar): 1 mol = 24.8 L.

Frequently Asked Questions

What is Avogadro Law? ▾

V/n = constant at constant T and P. Named for Amedeo Avogadro. Equal volumes of ideal gases at same T,P contain equal numbers of molecules, regardless of gas identity.

What is the molar volume at STP? ▾

STP = 0 C (273.15 K), 1 atm. Molar volume = 22.414 L/mol. At SATP (25 C, 1 bar): 24.789 L/mol.

How does Avogadro Law apply to reactions? ▾

For gas-phase reactions: volume ratio = mole ratio at same T,P. H2(g) + Cl2(g) to 2HCl(g): 1 vol H2 + 1 vol Cl2 gives 2 vol HCl.

What is Avogadro number? ▾

Na = 6.022x10^23 mol^-1. Number of entities per mole. Found experimentally; consistent with atomic theory.

Why does doubling moles double volume? ▾

At constant T and P, the pressure exerted by gas molecules must remain constant. More molecules: need more volume to maintain same pressure.

Related Chemistry Calculators

Formula Explorer connections

Interpretation: This relationship connects pressure, volume, temperature, amount or phase composition for gases and volatile mixtures. Assumption: Use absolute temperature and compatible pressure-volume units. Ideal behavior weakens at high pressure, low temperature, strong intermolecular attraction or near phase change.

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