Question

In the reaction A \( \rightarrow \) Products, when the concentration of A was reduced from \( 2.4 \times 10^{-2} \) M to \( 1.2 \times 10^{-2} \) M, the rate decreased 8 times at the same temperature. The order of the reaction is

• A. 0
• B. 1
• C. 2
• D. 3
• E. 0.5

Hint:

If concentration halves and rate becomes 1/8 ⇒ order = 3

Answer 1

The Correct Option is D

Concept: Rate law dependence
\[ \text{Rate} \propto [A]^n \] ---

Step 1: Concentration change
\[ \frac{[A]_2}{[A]_1} = \frac{1.2}{2.4} = \frac{1}{2} \] ---

Step 2: Rate change
\[ \frac{r_2}{r_1} = \frac{1}{8} \] ---

Step 3: Apply relation
\[ \left(\frac{1}{2}\right)^n = \frac{1}{8} \] \[ \left(\frac{1}{2}\right)^3 = \frac{1}{8} \] \[ n = 3 \] --- Final Answer: \[ \boxed{3} \]