How this calculator works
Copy coefficients from an already balanced equation, preserving species order. The ratio applies to molecules or moles, while masses also depend on each molar mass. Select the known species by its position, then scale every coefficient by the same reaction extent. Mass mode parses formulas with the shared IUPAC atomic-weight table and reports molecular atom counts. The calculation describes amounts consumed or formed, not leftovers when a limiting reagent is exhausted.
Formula
Species amount ni = coefficient i x extent. Extent = known moles/known coefficient. Mass i = ni Mi.
Worked example
For N2 + 3H2 -> 2NH3, 2 mol N2 corresponds to 6 mol H2 and 4 mol NH3. For 2H2 + O2 -> 2H2O, 3 mol O2 corresponds to 6 mol each of H2 and H2O.
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Frequently asked questions
Is a mass ratio the same as a molar ratio?
Usually not. Multiply each coefficient by its species molar mass to compare masses.
Can I enter molecules instead of moles?
The numerical ratio is the same, but the amount inputs and tables are labelled in moles.
Does this identify the limiting reactant?
No. Supply the limiting amount or compare the extents supported by all available reactants.