A State of Dynamic Balance

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Equilibrium Noun

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[ee-kwuh-lib-ree-uhm]

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Equilibrium

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A state in which opposing processes occur at equal rates, resulting in a dynamic balance with no net change.

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Example: Two people in a tug-of-war pull with equal and opposite force, so neither moves, demonstrating a state of equilibrium or balanced forces.

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Spontaneous Reaction Noun

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[spon-tey-nee-uhs ree-ak-shuhn]

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Spontaneous Reaction

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A reaction that proceeds to form products under a given set of conditions without a continuous external input of energy.

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Example: Mixing iron powder and hydrochloric acid causes a chemical reaction that produces gas bubbles on its own, without needing continuous energy from an outside source.

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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 that can proceed in both the forward direction (reactants to products) and the reverse direction (products to reactants).

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Example: This graph shows that in a reversible reaction, reactants decrease and products increase until their concentrations become constant, reaching a state of dynamic equilibrium.

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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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The state where forward and reverse reaction rates are equal, causing reactant and product concentrations to remain constant over time.

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Example: This graph shows that in a chemical reaction, equilibrium is reached when the amounts of reactants (N₂O₄) and products (NO₂) stop changing over time.

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Closed System Noun

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[klohzd sis-tuhm]

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Closed System

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A physical system that does not allow the transfer of matter in or out, which is necessary for reaching equilibrium.

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Example: This diagram shows nutrient cycling, a process in a closed system where matter like carbon (CO2) and water is constantly reused, maintaining a dynamic balance.

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Sublimation Noun

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[suhb-luh-mey-shuhn]

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Sublimation

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The phase transition of a substance directly from the solid to the gas state, without passing through the liquid state.

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Example: This diagram shows sublimation as the process where particles in a solid state, which are tightly packed, change directly into a gaseous state, where they are far apart.

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Law of Chemical Equilibrium Noun

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

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Law of Chemical Equilibrium

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A principle stating that at a given temperature, a chemical system reaches a state where a specific ratio of concentrations is constant.

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Example: This graph shows that in a chemical equilibrium, the forward reaction slows down as the backward reaction speeds up, until both reactions occur at the same rate.

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Equilibrium Constant Expression Noun

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[ee-kwuh-lib-ree-uhm kon-stuhnt ik-spresh-uhn]

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Equilibrium Constant Expression

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The ratio of product concentrations to reactant concentrations, with each raised to the power of its coefficient in the balanced equation.

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Example: This image shows how to write the equilibrium constant expression (K) for a general reversible reaction, relating the concentration of products to the concentration of reactants.

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Equilibrium Constant (Keq) Noun

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[ee-kwuh-lib-ree-uhm kon-stuhnt]

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Equilibrium Constant (Keq)

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The numerical value of the equilibrium constant expression, indicating the extent of a reaction at a specific temperature.

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Example: The equilibrium constant (K) is calculated from the ratio of the concentration of products to the concentration of reactants in a chemical reaction that has reached a state of balance.

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Homogeneous Equilibrium Noun

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[hoh-muh-jee-nee-uhs ee-kwuh-lib-ree-uhm]

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Homogeneous Equilibrium

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An equilibrium state in which all reactants and products exist in the same single physical phase, such as all gases.

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Example: This diagram shows a reversible reaction (double arrow) where reactants and products are all in the same state (represented by similar spheres), defining homogeneous equilibrium.