Percent Yield Calculator

The Four Steps

1. Balance the equation. The calculator does it for you: Si + N₂ → Si₃N₄ becomes 3Si + 2N₂ → Si₃N₄.
2. Convert each reactant to moles. 2.00 g Si ÷ 28.086 g/mol = 0.0712 mol; 1.50 g N₂ ÷ 28.014 g/mol = 0.0535 mol.
3. Find how much product each could make. 0.0712 mol Si × (1 Si₃N₄ / 3 Si) = 0.0237 mol; 0.0535 mol N₂ × (1 / 2) = 0.0268 mol. Silicon makes less, so it is the limiting reactant.
4. Theoretical yield and percent yield. 0.0237 mol × 140.286 g/mol = 3.33 g of Si₃N₄. If you actually collected, say, 3.00 g, the percent yield would be 3.00 ÷ 3.33 × 100.

The nitrogen left over is 0.17 g of the 1.50 g. Atomic masses come from the site’s molar mass calculator (159.602 g/mol for CuSO₄, where OpenStax rounds to 159.62). Here both give 0.5072 g of copper, but other problems can differ from a textbook answer in the last significant figure.

OpenStax Examples, Reproduced

Check the hydrogen problem by ratio: 5.00 g H₂ is 2.48 mol and would need 1.24 mol of O₂, but 10.0 g O₂ is only 0.313 mol, so oxygen runs out first even though more grams of it were used.

Why Yields Fall Short

Real reactions rarely reach 100%: some product stays on glassware or filter paper, side reactions use reactants, reactions can stop before completion, and purification loses some material. A yield above 100% almost always means the product is still wet or contains impurities.

Common Mistakes

• Picking the limiting reactant by mass. Compare moles of product, not grams of reactant; oxygen limits the hydrogen problem despite its larger mass.
• Skipping the mole ratio. Moles of Si do not equal moles of Si₃N₄; divide by 3.
• Using an unbalanced equation. Every coefficient changes the ratio.
• Using the excess reactant for the theoretical yield. Only the limiting reactant sets it.
• Flipping the fraction. Percent yield is actual over theoretical, so it is normally below 100%.

What This Calculator Does Not Cover

It takes masses in grams of pure reactants. For solutions, convert volume and molarity to moles first (the molarity calculator helps); for gases, use the ideal gas law. It assumes a single reaction with no side products.

Frequently Asked Questions

How to Use This Calculator

1. Enter the reaction — with formulas, e.g. Si + N2 = Si3N4; it is balanced automatically.
2. Enter reactant masses — as formula = grams; leave out reactants that are in excess.
3. Choose the product — the one whose yield you want.
4. Add the actual yield — to get percent yield; otherwise you get the theoretical yield and limiting reactant.