Percent Yield
Percent yield is the ratio of the actual yield of a chemical reaction (the amount of product experimentally obtained) to the theoretical yield (the maximum amount predicted by stoichiometry), expressed as a percentage. Values below 100% indicate losses due to incomplete reactions, side reactions, product loss during purification, or measurement errors. Percent yield is a key quality metric in synthetic chemistry, pharmaceuticals, and industrial chemical production.
Key Formula
% Yield = (Actual Yield / Theoretical Yield) × 100%
LaTeX: \%\, \text{Yield} = \dfrac{\text{Actual Yield}}{\text{Theoretical Yield}} \times 100\%
| Symbol | Meaning | Unit |
|---|---|---|
| Actual Yield | Mass of product actually obtained in the experiment | g |
| Theoretical Yield | Maximum mass of product predicted by stoichiometry | g |
| % Yield | Percent yield of the reaction | % |
Worked Example
Problem
A student reacts 10.0 g of iron (Fe) with excess sulfur (S) to form iron(II) sulfide (FeS). The theoretical yield is 14.4 g of FeS, but the student obtains only 11.7 g. What is the percent yield?
Solution
Step 1: Identify values: Actual yield = 11.7 g; Theoretical yield = 14.4 g. Step 2: Apply the formula: % Yield = (11.7 / 14.4) × 100%. Step 3: Calculate: % Yield = 0.8125 × 100% = 81.25%.
Answer
Percent yield = 81.3%
Typical Percent Yields in Chemical Synthesis
| Reaction Type | Typical % Yield | Primary Cause of Loss | Industry Example |
|---|---|---|---|
| Simple precipitation | 85–95% | Filtration losses | Barium sulfate production |
| Organic synthesis (1 step) | 70–90% | Side reactions | Aspirin synthesis |
| Multi-step organic | 30–60% | Cumulative losses | Drug synthesis |
| Industrial catalysis | 50–80% | Incomplete conversion | Haber process (ammonia) |
| Enzymatic reactions | 60–99% | Enzyme specificity | Pharmaceutical APIs |
Interactive Tools
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Related Terms
Stoichiometry
Stoichiometry is the branch of chemistry that deals with the quantitative relationships between reactants and products in chemical reactions. It uses balanced chemical equations to calculate the masses, volumes, or moles of substances involved in a reaction. Stoichiometry is fundamental to industrial chemistry, pharmaceutical manufacturing, and any process requiring precise control of chemical quantities.
Mole (chemistry)
The mole is the SI base unit for the amount of substance, defined as exactly 6.02214076 × 10²³ elementary entities (atoms, molecules, ions, or other particles). It provides chemists with a practical bridge between the atomic scale and macroscopic, measurable quantities in the laboratory. One mole of any substance contains the same number of particles, making it the universal counting unit of chemistry.
Molar Mass
Molar mass is the mass of one mole of a substance, expressed in grams per mole (g/mol), and numerically equal to the substance's relative atomic or molecular mass in unified atomic mass units. It is calculated by summing the atomic masses of all atoms in one formula unit of the substance, using values from the periodic table. Molar mass is the essential conversion factor between grams (measurable in the lab) and moles (used in chemical calculations).
From Latin "per centum" (by the hundred) and Old English "gield" (payment, return). The concept formalised in 19th-century analytical chemistry as chemists began quantifying reaction efficiency.