Percent Yield Calculator

Calculate percent yield to measure reaction efficiency, or find actual/theoretical yield based on experimental data. This calculator supports three modes: calculating percent yield from actual and theoretical values, finding actual yield from percent and theoretical, or determining theoretical yield from actual and percent.

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Percent Yield Formulas: 1. PERCENT YIELD (most common): Percent Yield = (Actual Yield ÷ Theoretical Yield) × 100% Where: - Actual Yield = amount of product obtained in the lab (g) - Theoretical Yield = maximum possible amount (g) from stoichiometry 2. ACTUAL YIELD: Actual Yield = (Percent Yield ÷ 100) × Theoretical Yield Use when you know the efficiency and maximum possible yield. 3. THEORETICAL YIELD: Theoretical Yield = (Actual Yield ÷ Percent Yield) × 100 Use when you know what you got and the efficiency. CALCULATING THEORETICAL YIELD FROM LIMITING REAGENT: Step 1: Find moles of limiting reagent Moles = Mass ÷ Molar Mass Step 2: Use stoichiometry (mole ratio from balanced equation) Product Moles = (Limiting Moles ÷ Limiting Coeff) × Product Coeff Step 3: Convert to mass Theoretical Yield = Product Moles × Product Molar Mass EFFICIENCY RATINGS: - 90-100%: Excellent (rare, check for errors if >100%) - 70-89%: Good (typical for many reactions) - 50-69%: Moderate (acceptable for complex reactions) - 30-49%: Low (common in multi-step syntheses) - <30%: Very Low (needs optimization)
Example 1: Calculate Percent Yield Reaction: 2H₂ + O₂ → 2H₂O Given: - Theoretical yield = 50.0 g H₂O - Actual yield = 42.5 g H₂O (measured in lab) Percent Yield = (42.5 ÷ 50.0) × 100% = 85.0% Product loss = 50.0 - 42.5 = 7.5 g Rating: Good efficiency Example 2: Calculate Actual Yield You expect 75% yield from a reaction with theoretical yield 60.0 g. Actual Yield = (75 ÷ 100) × 60.0 = 45.0 g You should obtain approximately 45.0 g of product. Example 3: Calculate Theoretical Yield You obtained 30.0 g product with 65% yield. Theoretical Yield = (30.0 ÷ 65) × 100 = 46.2 g Maximum possible was 46.2 g. Example 4: Full Calculation from Limiting Reagent Reaction: N₂ + 3H₂ → 2NH₃ Given: - Limiting reagent: 14.0 g N₂ (MM = 28.014 g/mol, coeff = 1) - Product: NH₃ (MM = 17.031 g/mol, coeff = 2) - Actual yield obtained: 15.0 g NH₃ Step 1: Theoretical Yield - Moles N₂ = 14.0 ÷ 28.014 = 0.500 mol - Moles NH₃ = (0.500 ÷ 1) × 2 = 1.00 mol - Theoretical = 1.00 × 17.031 = 17.0 g Step 2: Percent Yield - Percent = (15.0 ÷ 17.0) × 100% = 88.2% - Rating: Good Example 5: Checking for Errors Theoretical yield = 25.0 g Actual yield = 27.5 g Percent Yield = (27.5 ÷ 25.0) × 100% = 110% ⚠️ WARNING: Over 100% indicates: - Product contains impurities (water, solvent) - Measurement error - Calculation mistake - Need to dry or purify product

What is percent yield?

Percent yield is the ratio of actual yield (what you actually obtained in the lab) to theoretical yield (maximum possible based on stoichiometry) expressed as a percentage. It measures reaction efficiency.

Why is percent yield usually less than 100%?

Several factors reduce yield: incomplete reactions, side reactions producing other products, product loss during purification/transfer, measurement errors, and reversible reactions reaching equilibrium before completion.

Can percent yield exceed 100%?

In theory, no. A yield over 100% indicates errors: impure product (containing water, solvents, or byproducts), measurement mistakes, or calculation errors. Always verify if you get >100%.

How do I calculate theoretical yield?

Use stoichiometry with the limiting reagent. Convert limiting reagent mass to moles, use mole ratios from the balanced equation, then convert product moles to mass using its molar mass.

What is a good percent yield in the lab?

It varies by reaction. Simple reactions might achieve 80-95%. Complex organic syntheses with multiple steps often yield 30-70%. Industrial processes are optimized for higher yields due to cost considerations.

How does percent yield differ from percent purity?

Percent yield measures how much product formed compared to the theoretical maximum. Percent purity measures how much of your sample is the desired product versus impurities. Both are important quality metrics.

What factors affect percent yield?

Reaction completeness, side reactions, product stability, separation/purification efficiency, experimental technique, temperature, pressure, catalyst presence, and reversible reaction equilibrium all impact yield.

Should I use actual or theoretical yield first in calculation?

The formula is (Actual Yield ÷ Theoretical Yield) × 100%. Actual is the numerator (what you got), theoretical is the denominator (what was possible). Order matters in division.

How do I improve percent yield?

Optimize reaction conditions (temperature, time, concentration), use excess reagent for expensive limiting reagents, employ catalysts, minimize product loss during transfers, improve purification techniques, and prevent side reactions.

What is the relationship between limiting reagent and percent yield?

The limiting reagent determines theoretical yield (maximum product possible). Actual yield is measured experimentally. Percent yield = (Actual ÷ Theoretical) × 100%, showing how efficiently the limiting reagent was converted to product.

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