Limiting Reactants

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Limiting Reactant Noun

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[lim-it-ing ree-ak-tant]

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Limiting Reactant

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

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Example: This image shows that when making brownies, the brownie mix runs out before the eggs do, limiting how many brownies can be made.

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Excess Reactant Noun

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[ek-ses ree-ak-tant]

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Excess Reactant

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The reactant in a chemical reaction that remains after the limiting reactant is completely consumed and the reaction has stopped.

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Example: In a reaction to make water, all the oxygen atoms are used up, but some hydrogen atoms are left over. The leftover hydrogen is the excess reactant.

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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 reactants, as calculated from the limiting reactant.

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Example: Combining 1 Kg of hydrogen and 1 Kg of oxygen should theoretically yield 2 Kg of water, but the actual yield in a real experiment is often less.

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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 amount of product that is actually obtained when a chemical reaction is carried out in a laboratory or industrial setting.

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Example: This image shows the formula for percent yield, where 'actual yield' is the measured amount of product (13.74 g) obtained from a chemical reaction.

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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, which measures the efficiency of a reaction.

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Example: This image shows the formula to calculate percent yield, which is the actual amount of product you get from a reaction divided by the theoretical maximum.

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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 area of chemistry that involves using relationships between reactants and products in a chemical reaction to determine quantitative data.

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Example: This image shows a calculation to find the mass of a product (CO2) from a given amount of a reactant (C3H8), a key skill in stoichiometry.

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Mole Noun

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[mohl]

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Mole

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The SI unit for the amount of a substance, representing approximately 6.022 x 10^23 particles of that substance.

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Example: This image shows that one mole of different elements, like carbon (12.0 g) and lead (207 g), has a different mass and volume.

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Molar Mass Noun

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[moh-ler mas]

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Molar Mass

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The mass of one mole of a substance, typically expressed in grams per mole (g/mol), used to convert between mass and moles.

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Example: This image shows how to find the molar mass of a water molecule (H₂O) by adding the atomic masses of its individual atoms: two hydrogen and one oxygen.

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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 from the coefficients of a balanced chemical equation relating the amounts in moles of any two substances.

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Example: This balanced chemical equation shows that 1 molecule of methane reacts with 2 molecules of oxygen. This 1:2 relationship is the mole ratio.

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Avogadro's Constant Noun

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[av-uh-gah-drohz kon-stuhnt]

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Avogadro's Constant

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The number of constituent particles per mole of a substance, with a value of approximately 6.022 x 10^23 mol⁻¹.

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Example: This image shows Avogadro's number (6.02 x 10^23) is the number of items in one mole and gives an example of converting moles to atoms.