AP Chemistry 5.1-5.3 Rate Laws

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What is a rate law?

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A rate law is an equation that relates the rate of a chemical reaction to the concentration of its reactants, typically in the form: Rate = k[A]^m[B]^n, where k is the rate constant, and m and n are the reaction orders.

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What is the rate constant (k)?

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The rate constant (k) is a proportionality factor in the rate law that is specific to a particular reaction at a given temperature. It indicates the speed of the reaction.

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Define reaction order.

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Reaction order is the exponent to which the concentration of a reactant is raised in the rate law. It indicates how the rate of reaction depends on the concentration of that reactant.

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What does a zero-order reaction mean?

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In a zero-order reaction, the rate of reaction is constant and independent of the concentration of the reactants. The rate law is: Rate = k.

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How do you determine the order of a reaction experimentally?

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The order of a reaction can be determined by measuring the rate of reaction at different concentrations of reactants and analyzing the data using methods such as the method of initial rates or integrated rate laws.

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What is the method of initial rates?

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The method of initial rates involves measuring the initial rate of reaction for different initial concentrations of reactants to determine the reaction order.

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What is the significance of the rate exponent in a rate law?

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The rate exponent indicates how the rate of reaction changes with changes in the concentration of a reactant. For example, if the exponent is 2, doubling the concentration will quadruple the rate.

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What is a first-order reaction?

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In a first-order reaction, the rate is directly proportional to the concentration of one reactant. The rate law is: Rate = k[A].

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What is a second-order reaction?

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In a second-order reaction, the rate is proportional to the square of the concentration of one reactant or to the product of the concentrations of two reactants. The rate law can be: Rate = k[A]^2 or Rate = k[A][B].

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How do you calculate the rate constant (k) from experimental data?

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To calculate k, rearrange the rate law to solve for k: k = Rate / [A]^m[B]^n, using the measured rate and concentrations.