Stoichiometric Calculations

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

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Example: This balanced chemical equation shows one methane molecule reacting with two oxygen molecules, demonstrating the fixed quantitative relationships (ratios) at the heart of stoichiometry.

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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 process.

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Example: The substances on the left side of the arrow, methane (CH4) and oxygen (O2), are the reactants that combine to start the chemical reaction.

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Product Noun

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[prod-uhkt]

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Product

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

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Example: In a chemical reaction, the starting materials (reactants) transform into new substances called products, shown here on the right side of the arrow.

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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 that relates the moles of any two substances in the reaction.

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Example: This image shows that for every 2 molecules of hydrogen (H₂) and 1 molecule of oxygen (O₂), 2 molecules of water (H₂O) are formed, visually explaining the 2:1:2 mole ratio.

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Balanced Chemical Equation Noun

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

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Balanced Chemical Equation

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A chemical equation where the number of atoms for each element is equal on both reactant and product sides.

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Example: A chemical reaction in a closed flask shows the total mass stays the same. A balanced chemical equation represents this, proving that no atoms are lost or gained.

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Mole Noun

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[mohl]

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Mole

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The SI base unit for measuring the amount of a substance, equal to approximately 6.022 x 10^23 particles.

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Example: One mole represents a specific quantity (6.022 x 10^23 particles) and has a measurable mass, shown here as 12 grams of carbon.

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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 in grams of one mole of a pure substance, used to convert between mass and moles.

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Example: The molar mass of a water molecule (H₂O) is calculated by adding the mass of two hydrogen atoms and one oxygen atom together.

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Limiting Reactant Noun

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

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Limiting Reactant

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

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Example: In this reaction, all the oxygen atoms (O) are used up to make water, so oxygen is the limiting reactant. Some hydrogen atoms (H) are left over.

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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 product obtained from a reaction to the theoretical maximum amount, expressed as a percentage.

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Example: This image shows the formula for percent yield, which compares the actual amount of product made in a reaction to the maximum theoretical amount possible.

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Decomposition Noun

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[dee-kom-puh-zish-uhn]

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Decomposition

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A type of chemical reaction in which a single compound breaks down into two or more simpler substances.

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Example: This diagram shows one compound, Zinc Carbonate, breaking down into two simpler substances, Zinc Oxide and Carbon Dioxide, which is a decomposition reaction.