Question

For a reaction A → B, the concentration of A decreases from 0.8 M to 0.2 M in 10 minutes. If the rate constant is 0.1 min⁻¹, what is the order of the reaction?

• A. 0
• B. 1
• C. 2
• D. 3

Hint:

For first-order reactions, use the equation \( \ln \frac{[A_0]}{[A]} = kt \) to calculate the reaction order.

Answer 1

The Correct Option is B

The reaction rate law is expressed as: \[ \text{Rate} = k[A]^n, \] where \( n \) denotes the reaction order and \( k \) represents the rate constant. For a first-order reaction, the integrated rate law is: \[ \ln \frac{[A_0]}{[A]} = kt, \] with initial concentration \( [A_0] = 0.8 \, \text{M} \), final concentration \( [A] = 0.2 \, \text{M} \), and time \( t = 10 \, \text{minutes} \). Substituting these values yields: \[ \ln \frac{0.8}{0.2} = 0.1 \times 10. \] Upon simplification: \[ \ln 4 = 1. \] This result confirms the reaction is first-order. The determined order is: \[ \boxed{1}. \]