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Stoichiometry Calculator
Convert between any two substances in a reaction. Type the equation (it is balanced for you), enter what you know in grams, moles, particles, litres of gas or a solution volume, and get the answer in the unit you need. A full table shows every reactant and product, with each step explained.
How to solve stoichiometry problems
- Balance the equation. The coefficients give the mole ratio.
- Convert what you are given to moles: grams ÷ molar mass, particles ÷ 6.022 × 10²³, litres of gas ÷ 22.4 L/mol (STP), or volume of solution × molarity.
- Apply the mole ratio: mol B = mol A × (coefficient of B ÷ coefficient of A).
- Convert moles of B into the unit you need (grams, particles, litres).
grams A → ÷ M(A) → mol A → × (b/a) → mol B → × M(B) → grams B
| Convert | To moles | From moles |
|---|---|---|
| Mass (g) | ÷ molar mass | × molar mass |
| Particles | ÷ 6.022 × 10²³ | × 6.022 × 10²³ |
| Gas volume (L) | ÷ 22.414 L/mol (STP) | × 22.414 L/mol |
| Solution volume (L) | × molarity | ÷ molarity |
Worked examples
Mass to mass
How much O₂ burns 10.0 g propane? C₃H₈ + 5O₂ → 3CO₂ + 4H₂O. 10.0/44.10 = 0.2268 mol × 5 = 1.134 mol × 32.00
36.3 g O₂
Moles to gas volume
1 mol Fe₂O₃ + 3CO → 2Fe + 3CO₂ gives 3 mol CO₂ × 22.414 L/mol
67.2 L CO₂ at STP
Solution stoichiometry
25.0 mL of 0.200 M H₂SO₄ = 5.00 mmol, which needs 2 × 5.00 = 10.0 mmol NaOH × 40.00 g/mol
0.400 g NaOH
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Open MolDraw editorFrequently asked questions
What is stoichiometry?
Stoichiometry uses the mole ratios in a balanced chemical equation to work out how much of one substance reacts with, or forms from, a given amount of another.
How do you do grams-to-grams stoichiometry?
Convert grams of A to moles (÷ molar mass), multiply by the mole ratio (coefficient of B ÷ coefficient of A), then convert moles of B to grams (× molar mass of B).
What is the mole ratio?
The ratio of coefficients in the balanced equation. In 2H₂ + O₂ → 2H₂O the mole ratio of H₂ to O₂ is 2:1, so 4 mol H₂ needs 2 mol O₂.
What molar volume should I use for gases?
22.414 L/mol at STP (0 °C, 1 atm), 22.711 L/mol at IUPAC STP (0 °C, 1 bar) and 24.465 L/mol at 25 °C and 1 atm. For other conditions use V = nRT/P, which the custom option does.
How do I handle solutions?
Moles = molarity × volume in litres. For example, 25.0 mL of 0.200 M = 0.00500 mol. Then apply the mole ratio as usual.
What if one reactant runs out?
This calculator converts between two species, assuming everything else is in excess. If you have amounts of two or more reactants, use the theoretical yield calculator to find the limiting reagent.