Question

A zero-order reaction has a rate that is:

• A. Independent of reactant concentration
• B. Proportional to the reactant concentration
• C. Proportional to the square of the reactant concentration
• D. Inversely proportional to reactant concentration

Hint:

Zero-order reactions proceed at a constant rate — the concentration of the reactant doesn't influence the speed of reaction.

Answer 1

The Correct Option is A

In chemical kinetics, the order of a reaction indicates how the rate depends on the concentration of the reactants.
For a zero-order reaction, the rate law is expressed as:
\[ \text{Rate} = k \]
where $k$ is the rate constant.
This means that the rate of reaction is constant and independent of the concentration of the reactants.
No matter how much reactant is present, the rate of reaction remains the same until the reactant is exhausted.
Such behavior is commonly observed in reactions that occur on catalytic surfaces or where the catalyst becomes saturated — beyond a certain concentration, additional reactant does not increase the rate.
Let’s examine the incorrect options:
- (2) Proportional to concentration: This describes a first-order reaction.
- (3) Proportional to the square: Describes a second-order reaction.
- (4) Inversely proportional: This is not characteristic of any common reaction order.
Thus, the rate of a zero-order reaction is independent of the reactant concentration.