How to use the limiting reagent calculator
Identify the limiting reactant for A + B → product. Enter moles of a, coefficient of a, moles of b, coefficient of b in the fields above; the reaction extent (limiting), limiting reagent, excess a left, excess b left are computed instantly and plotted on the chart so you can see how the answer changes.
Formula
Variables
- nA — Moles of A (mol)
- cA — Coefficient of A
- nB — Moles of B (mol)
- cB — Coefficient of B
Worked example
With moles of a = 2 mol, coefficient of a = 2, moles of b = 1.5 mol, coefficient of b = 1, the calculator gives reaction extent (limiting) ≈ 1 mol; limiting reagent ≈ A; excess a left ≈ 0 mol; excess b left ≈ 0.5 mol.
Frequently asked questions
What is the formula for the limiting reagent calculation?
Reaction extent (limiting) (mol) = min(nA / cA,nB / cB). Limiting reagent = nA / cA<nB / cB?"A":(nA / cA>nB / cB?"B":"Neither (stoichiometric)"). Excess A left (mol) = nA-cA × [Reaction extent (limiting)]. Excess B left (mol) = nB-cB × [Reaction extent (limiting)]. Here nA is moles of a (mol), cA is coefficient of a, nB is moles of b (mol), cB is coefficient of b.
What inputs do I need for the limiting reagent calculator?
You need moles of a in mol, coefficient of a, moles of b in mol, coefficient of b. Each field is pre-filled with a typical example so you can see how the result responds as you edit the numbers.
How do I use this calculator?
Type values into the input fields. Results and the chart update instantly. Use Reset to restore the example values, Copy results to paste them elsewhere, or Share to copy a link that preserves your inputs.
Is the result exact?
Calculations use standard formulas and double-precision arithmetic, then display about seven significant figures. Real-world measurements carry uncertainty, so treat results as estimates unless your inputs are exact.