Reaction Rate Laws

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Reaction Rate Law Noun

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[ree-ak-shun rayt law]

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Reaction Rate Law

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An equation expressing the relationship between the rate of a chemical reaction and the concentration of reactants at a given temperature.

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Example: This image shows the mathematical equation for the reaction rate law, relating the reaction rate to the concentration of reactants [A] and [B].

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Specific Rate Constant (k) Noun

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[spuh-sif-ik rayt kon-stunt]

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Specific Rate Constant (k)

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A numerical value that relates the reaction rate and the concentrations of reactants at a specific temperature for a unique reaction.

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Example: The image shows that in a chemical reaction with multiple steps, the slowest step (labeled with k₁) determines the overall speed, which is represented by 'k' in the final rate equation.

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Reaction Order Noun

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[ree-ak-shun or-der]

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Reaction Order

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The exponent for a reactant in the rate law, which defines how the rate is affected by that reactant's concentration.

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Example: This table shows that for a zero-order reaction, changing the concentration of a reactant does not change how fast the reaction happens.

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First-Order Reaction Noun

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[furst or-der ree-ak-shun]

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First-Order Reaction

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A reaction where the rate is directly proportional to the concentration of a single reactant raised to the first power.

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Example: This graph shows that in a first-order reaction, the concentration of a substance decreases over time, with the reaction slowing down as less substance is available.

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Zero-Order Reactant Noun

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[zeer-oh or-der ree-ak-tant]

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Zero-Order Reactant

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A reactant whose concentration change has no effect on the rate of the reaction, having an exponent of zero.

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Example: This graph shows that for a zero-order reaction, the speed (rate) of the reaction stays constant, no matter how much reactant you have.

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Overall Reaction Order Noun

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[oh-ver-awl ree-ak-shun or-der]

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Overall Reaction Order

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The sum of the orders for the individual reactants in the rate law, indicating the reaction's total dependency on concentration.

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Example: This table shows experimental data. By comparing how changing reactant amounts affects the reaction speed, scientists can calculate the overall reaction order.

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Initial Rate Noun

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[in-ish-ul rayt]

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Initial Rate

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The instantaneous reaction rate measured at the moment the reactants are mixed, when their initial concentrations are precisely known.

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Example: This graph shows that a chemical reaction is fastest at the beginning (initial rate), where the curve measuring product volume over time is steepest.

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Method of Initial Rates Noun

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[meth-ud uv in-ish-ul rayts]

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Method of Initial Rates

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An experimental method to find the reaction order by comparing initial rates of a reaction with varying reactant concentrations.

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Example: This table shows how scientists measure reaction speed (Initial Rate) by changing the starting amount ([A] or [B]) of one chemical at a time.