Question

For the reaction $X \rightarrow Y$, the concentrations of $X$ are 1.2M, 0.6M, 0.3M and 0.15M at 0, 1, 2 and 3 hours respectively. The order of the reaction is

• A. zero
• B. half
• C. one
• D. two
• E. three

Hint:

If concentration halves in equal time intervals → reaction is first order.

Answer 1

The Correct Option is C

Concept: For first-order reactions:
• Concentration decreases exponentially
• Equal time → concentration reduces by same fraction

Step 1: Observe concentration pattern. \[ 1.2 \rightarrow 0.6 \rightarrow 0.3 \rightarrow 0.15 \]

Step 2: Check ratio. \[ \frac{0.6}{1.2} = \frac{0.3}{0.6} = \frac{0.15}{0.3} = \frac{1}{2} \]

Step 3: Interpretation.
• Concentration halves every hour
• This means constant half-life
• Property of first-order reaction Conclusion: \[ \boxed{\text{Order = 1}} \]