First order description?

First order description?

• A. Rate is independently of concentration.
• B. Rate is directly proportional to concentration.
• C. Rate is proportional to the square of concentration.
• D. Rate is proportional to the reciprocal of concentration.

Answer: (B)

In first-order kinetics the rate law has the form rate = k[A], so the rate scales directly with the concentration of the reactant. This means doubling the concentration doubles the rate, tripling it triples the rate, and so on. The key point is the linear relationship between rate and [A], which distinguishes first-order behavior from zero-order (rate independent of [A]), second-order (rate ∝ [A]^2), or an inverse dependence (rate ∝ 1/[A]). Hence, the rate is directly proportional to concentration.

In first-order kinetics the rate law has the form rate = k[A], so the rate scales directly with the concentration of the reactant. This means doubling the concentration doubles the rate, tripling it triples the rate, and so on. The key point is the linear relationship between rate and [A], which distinguishes first-order behavior from zero-order (rate independent of [A]), second-order (rate ∝ [A]^2), or an inverse dependence (rate ∝ 1/[A]). Hence, the rate is directly proportional to concentration.