Stoichiometry Calculator
Unknown Substance (moles)
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Unknown Substance (grams)
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How Stoichiometry Works
Stoichiometry uses the mole ratios from a balanced chemical equation to calculate amounts of reactants and products. The coefficients in a balanced equation give the ratio: if 2A → 1B, then 2 moles of A produce 1 mole of B.
To use this calculator: enter the moles of the known substance, its coefficient in the balanced equation, and the coefficient of the unknown substance. The calculator computes moles of the unknown using: moles_unknown = moles_known × (coeff_unknown / coeff_known).
Stoichiometry is the quantitative backbone of chemistry. It's used in manufacturing to determine raw material needs, in pharmacology for drug dosing, and in environmental science for pollution calculations. Always start with a balanced equation.
Frequently Asked Questions
What is stoichiometry?
The calculation of quantities in chemical reactions using mole ratios from balanced equations. It predicts how much product forms or reactant is needed.
Why must equations be balanced?
Balanced equations obey the law of conservation of mass — atoms are neither created nor destroyed. Mole ratios only work with balanced equations.
What is a mole ratio?
The ratio of coefficients in a balanced equation. In 2H₂ + O₂ → 2H₂O, the H₂:O₂ ratio is 2:1 and H₂:H₂O ratio is 2:2 (or 1:1).
What is a limiting reagent?
The reactant that runs out first, limiting how much product can form. To find it, calculate how much product each reactant could produce — the smaller amount determines the limit.