Reversible Reactions and Equilibrium

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Reversible Reaction Noun

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[ri-vur-suh-buhl ree-ak-shuhn]

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Reversible Reaction

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A chemical reaction where products can react under ordinary conditions to re-form the original reactants, proceeding in both directions.

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Example: This diagram shows that reactants (left side) can form products (right side), and the products can also turn back into the original reactants, as shown by the two-way arrow.

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Forward Reaction Noun

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[for-werd ree-ak-shuhn]

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Forward Reaction

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The reaction in a reversible process that proceeds from left to right, converting reactants into products as typically written.

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Example: This diagram shows reactants on the left (methane and oxygen) transforming into products on the right, as indicated by the single forward-pointing arrow.

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Reverse Reaction Noun

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[ri-vurs ree-ak-shuhn]

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Reverse Reaction

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The reaction in a reversible process that proceeds from right to left, converting products back into the original reactants.

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Example: This diagram shows that reactants (A, B) can form products (C, D), and the products can also react to change back into the original reactants.

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Chemical Equilibrium Noun

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[kem-i-kuhl ee-kwuh-lib-ree-uhm]

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Chemical Equilibrium

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A state of balance in a reversible reaction where the rates of the forward and reverse reactions are exactly equal.

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Example: In a closed container, water evaporates and condenses at the same rate, reaching equilibrium. In an open container, water escapes and the process does not reverse.

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Equilibrium Position Noun

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[ee-kwuh-lib-ree-uhm puh-zish-uhn]

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Equilibrium Position

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The relative concentrations of reactants and products at equilibrium, indicating which direction of the reaction is favored at that point.

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Example: This image shows that the equilibrium position, like a ball in a valley, is the point of lowest energy for both a physical object and a chemical reaction mixture.

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Le Châtelier's Principle Noun

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[luh shaht-lee-eyz prin-suh-puhl]

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Le Châtelier's Principle

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A principle stating that if a system at equilibrium is disturbed, it will shift to counteract the disturbance and restore equilibrium.

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Example: This flowchart shows how a chemical reaction at balance (equilibrium) responds to a change (stress) by shifting forward or reverse to restore balance.

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Endothermic Adjective

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[en-doh-thur-mik]

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Endothermic

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Describes a chemical process or reaction that absorbs heat from its surroundings, causing a cooling effect on the environment.

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Example: Applying heat to water causes it to boil and turn into vapor. This process is endothermic because the water must absorb heat energy to change state.

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Exothermic Adjective

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[ek-soh-thur-mik]

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Exothermic

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Describes a chemical process or reaction that releases energy, usually in the form of heat, into its surroundings.

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Example: This potential energy diagram shows that in an exothermic reaction, the reactants start at a higher energy level than the products, releasing energy (heat).