A reaction A + B¡C obeys the following rate law: Rate = k3B42. (a) If [A] is doubled, how will the rate change? Will the rate constant change?

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1. 1. The rate law for the reaction is given as Rate = k[A][B]^2. This equation tells us that the rate of the reaction is directly proportional to the concentration of A and the square of the concentration of B.
2. 2. If the concentration of A is doubled, the rate of the reaction will also double. This is because the rate of the reaction is directly proportional to the concentration of A. So, if [A] is doubled, the rate will also double.
3. 3. The rate constant, k, is a proportionality constant that is specific to a particular reaction at a particular temperature. It does not change with changes in the concentrations of the reactants. Therefore, even if the concentration of A is doubled, the rate constant, k, will remain the same.
4. 4. So, in conclusion, if [A] is doubled, the rate of the reaction will double, but the rate constant will not change.
5. 5. Remember, the rate constant is only affected by changes in temperature, not by changes in the concentrations of the reactants.

Key Concepts

Rate Law

A rate law expresses the relationship between the rate of a chemical reaction and the concentration of its reactants. It is typically formulated as Rate = k[A]^m[B]^n, where k is the rate constant, and m and n are the orders of the reaction with respect to each reactant. Understanding the rate law is crucial for predicting how changes in concentration affect the reaction rate.

Order of Reaction

The order of a reaction refers to the exponent to which the concentration of a reactant is raised in the rate law. It indicates how sensitive the reaction rate is to changes in that reactant's concentration. In the given rate law, the order with respect to B is 4, meaning that if the concentration of B is increased, the rate will increase significantly, while changes in A do not affect the rate since it is not included in the rate law.

Rate Constant (k)

The rate constant (k) is a proportionality factor in the rate law that is specific to a particular reaction at a given temperature. It reflects the intrinsic speed of the reaction and does not change with the concentration of reactants. However, it can change with temperature or the presence of a catalyst. In this scenario, doubling the concentration of A will not affect the rate constant, as it is independent of reactant concentrations.