Limiting Reagent and Percent Yield

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Limiting Reagent Noun

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[lim-it-ing ree-ey-juhnt]

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Limiting Reagent

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The reactant that is completely consumed in a chemical reaction, determining the maximum amount of product that can be formed.

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Example: This image uses an analogy where the single loaf of bread is the limiting reagent, as there isn't enough to satisfy all the hands (the excess reagent).

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Excess Reagent Noun

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[ek-ses ree-ey-juhnt]

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Excess Reagent

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A reactant that remains after a chemical reaction stops because the limiting reagent has been completely used up.

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Example: Using a brownie recipe analogy, the image shows that after using all the brownie mix (limiting reactant), there are still eggs left over (excess reagent).

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Reactant Noun

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[ree-ak-tuhnt]

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Reactant

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A substance that is present at the start of a chemical reaction and is consumed during the reaction process.

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Example: This image shows the substances on the left (methane and oxygen) that are the starting materials, or reactants, in a chemical reaction.

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Product Noun

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[prod-uhkt]

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Product

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A new substance that is formed as the result of a chemical reaction between reactants.

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Example: In a chemical reaction, the new substances that are formed are called products. Here, carbon dioxide and water are the products of the reaction.

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Stoichiometry Noun

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[stoy-kee-om-i-tree]

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Stoichiometry

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The quantitative study of the relationships between the amounts of reactants used and products formed in a chemical reaction.

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Example: This image shows a balanced chemical reaction where one methane molecule (CH4) reacts with two oxygen molecules (2O2) to produce one carbon dioxide (CO2) and two water molecules (2H2O).

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Mole Ratio Noun

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[mohl rey-shee-oh]

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Mole Ratio

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A conversion factor derived from the coefficients of a balanced equation that relates the moles of any two substances.

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Example: This diagram shows that for every two molecules of hydrogen (H₂) and one molecule of oxygen (O₂), two molecules of water (H₂O) are produced.

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Theoretical Yield Noun

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[thee-uh-ret-i-kuhl yeeld]

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Theoretical Yield

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The maximum amount of product that can be produced from a given amount of reactant, calculated via stoichiometry.

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Example: This diagram shows reactants (1 Kg of Hydrogen and 1 Kg of Oxygen) combining to produce a product (Water), defining the theoretical yield as the maximum possible amount (2 Kg).

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Actual Yield Noun

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[ak-choo-uhl yeeld]

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Actual Yield

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The measured amount of product actually obtained from a chemical reaction when performed in a laboratory setting.

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Example: The image compares the maximum possible product (theoretical yield) to the product that is actually created (actual yield), showing the actual amount is often less.

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Percent Yield Noun

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[per-sent yeeld]

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Percent Yield

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The ratio of the actual yield to the theoretical yield, expressed as a percentage to measure a reaction's efficiency.

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Example: The formula for percent yield compares the actual amount of product from an experiment to the maximum possible amount (theoretical yield) to measure a reaction's efficiency.

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Side Reaction Noun

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[sahyd ree-ak-shuhn]

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Side Reaction

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An unintended chemical reaction that occurs alongside the main desired reaction, often reducing the yield of the main product.

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Example: This image illustrates a basic chemical reaction, showing reactants on the left turning into products on the right, but it does not depict an additional, unwanted 'side reaction'.