Stoichiometry Calculator
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Avogadro: 6.022 × 10²³ /mol · moles = grams ÷ molar mass · particles = moles × 6.022×10²³
Result
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What is stoichiometry?
Stoichiometry is the calculation of reactants and products in chemical reactions, using a balanced equation's mole ratios together with molar masses. The universal path is Grams A → Moles A → Moles B → Grams B.
Key concepts
- Mole — 6.022 × 10²³ particles (Avogadro's number)
- Molar mass — mass of one mole (g/mol)
- Mole ratio — the coefficient ratio from the balanced equation
- Limiting reactant — runs out first and caps the product
- Theoretical / actual / percent yield — predicted max, what you get, and their ratio × 100
- Gas at STP — 1 mole of any gas = 22.4 L at 0°C, 1 atm
Worked example — grams to moles
How many moles in 18 g of H₂O (molar mass 18.015 g/mol)? moles = 18 ÷ 18.015 = 0.999 ≈ 1 mol
Worked example — percent yield
Theoretical 50 g, actual 45 g → % yield = (45 ÷ 50) × 100 = 90%
Frequently asked
Divide the mass by the molar mass: moles = grams ÷ molar mass.
The reactant that runs out first. Convert each to moles, divide by its coefficient, and the smallest result is limiting.
Percent yield = (actual ÷ theoretical) × 100.
22.4 L per mole at 0°C and 1 atm.
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