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

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Example: This image shows four hands reaching for one loaf of bread. The bread is the limiting reactant because it will run out before all the hands get some.

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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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A reactant that is not completely used up and remains after a chemical reaction has stopped due to the limiting reactant.

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Example: This diagram uses a sandwich recipe to show that the excess reactant (bread) is the ingredient left over after the limiting reactant (cheese) is all used up.

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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 study and calculation of quantitative relationships between the amounts of reactants and products involved in chemical reactions.

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Example: This image shows a balanced chemical reaction, where one methane molecule (CH4) reacts with two oxygen molecules (O2) to form the exact amount of products with nothing left over.

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Product Noun

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[prod-ukt]

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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, reactants (methane and oxygen) are transformed into new substances called products (carbon dioxide and water).

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Reactant Noun

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[ree-ak-tant]

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Reactant

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A substance that takes part in and undergoes a chemical change during a reaction.

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Example: The image shows reactants, methane (CH₄) and oxygen (O₂), on the left side of the arrow, representing the starting substances in a chemical reaction.

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Conservation of Mass Noun

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[kon-ser-vey-shuhn of mas]

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Conservation of Mass

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The principle stating that atoms are not created or destroyed, meaning total reactant mass equals total product mass.

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Example: This diagram shows that the number of hydrogen (red) and oxygen (blue) atoms is the same before and after the chemical reaction, demonstrating conservation of mass.

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Balanced Chemical Equation Noun

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[bal-ansd kem-i-kuhl ih-kwey-zhuhn]

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Balanced Chemical Equation

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A representation of a chemical reaction where atom counts for each element are equal on both reactant and product sides.

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Example: This image shows that in a balanced chemical reaction, the number of atoms for each element is the same on both the starting (reactants) and ending (products) sides.

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Molar Mass Noun

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[moh-ler mas]

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Molar Mass

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A conversion factor representing the mass of one mole of a substance, typically expressed in grams per mole (g/mol).

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Example: Molar mass is calculated by summing the atomic masses of all atoms in a molecule, like the 6 carbon, 12 hydrogen, and 6 oxygen atoms in glucose.

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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 a balanced equation's coefficients that relates the molar amounts of any two substances in the reaction.

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Example: This diagram shows a balanced chemical reaction, visually representing the mole ratio: for every 1 molecule of methane, 2 molecules of oxygen are needed.

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Empirical Formula Noun

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[em-pir-i-kuhl fawr-myoo-luh]

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Empirical Formula

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A chemical formula that gives the simplest positive integer ratio of atoms of each element present in a compound.

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Example: This table shows how a molecular formula, the actual number of atoms in a molecule, is simplified to its empirical formula, the simplest whole-number ratio.