Problem 98 - Chemistry: An Atoms-Focused Approach

Question

If a reaction is zero order in a reactant, does that mean the reactant is never involved in collisions with other reactants? Explain your answer.

Step-by-Step Solution

Answer

Short Answer: No, a zero-order reaction does not indicate that the reactant is not involved in collisions with other reactants. Instead, it indicates that the rate of the reaction is not dependent on the concentration of that specific reactant, possibly due to factors such as the presence of a catalyst or a rate-limiting step that is independent of the concentration of that reactant.

Step 1: Understanding reaction order

Reaction order is an important aspect of chemical kinetics, which describes the relationship between the concentrations of reactants and the rate of a reaction. It tells us how the rate of a reaction changes with a change in the concentration of one of the reactants. The order of a reaction can be positive, negative, or zero, depending on the nature of the reaction.

Step 2: Definition of zero-order reaction

A zero-order reaction is a type of reaction where the rate of the reaction does not depend on the concentration of any of its reactants. Mathematically, it can be expressed as: rate = k, where k is the rate constant. Since the reaction rate is independent of the concentration of the reactants, the reaction proceeds at a constant rate until one or more reactants are depleted.

Step 3: Collision theory and chemical reactions

According to the collision theory, chemical reactions occur when the reactant molecules collide with one another with sufficient kinetic energy and proper orientation. Not all collisions result in a reaction, but the more frequently molecules collide, the more likely they are to react.

Step 4: Zero-order reaction and collision involvement

The fact that a reaction is zero-order does not mean that the reactant is not involved in collisions with other reactants. Instead, it indicates that the rate of the reaction is not dependent on the concentration of that specific reactant. This could be because the reaction is controlled by another factor, such as the presence of a catalyst or a rate-limiting step that is independent of the concentration of that reactant. In conclusion, a zero-order reaction does not imply that the reactant is never involved in collisions with other reactants. It simply means that the rate of the reaction is not influenced by the concentration of the reactant in question.