Final answer:
The relationship between reaction rate and reactant concentration is that the reaction rate depends on the concentration of reactants, while the rate constant is independent of it and only varies with temperature.
Step-by-step explanation:
The correct statement that characterizes the relationship between reaction rate and reactant concentration is: Reaction rate depends on [reactants], but the rate constant does not depend on [reactants].
The reaction rate usually increases with an increase in the concentration of the reactants because a higher concentration means more collisions among reactant molecules, leading to more frequent reaction events. However, the rate constant (k) is a proportionality constant that is independent of the concentration of reactants and is determined experimentally. It only changes with temperature.
The rate law for a chemical reaction includes the rate constant and shows the relationship between the reaction rate and the concentrations of reactants.
For example, in a first-order reaction, the reaction rate is directly proportional to the concentration of one reactant. In a second-order reaction, the rate is proportional to the square of the concentration of one reactant. The order of the reaction is determined by how the reaction rate depends on the concentration of the reactant.