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NEET CHEMISTRYMedium

The rate of a first-order reaction is 1.5×102 mol L1 min11.5 \times 10^{-2} \text{ mol L}^{-1} \text{ min}^{-1} at 0.5 M0.5 \text{ M} concentration of the reactant. The half-life of the reaction is:

A

23.1 min

B

8.73 min

C

7.53 min

D

0.383 min

Step-by-Step Solution

For a first-order reaction, the rate law is given by Rate=k[A]\text{Rate} = k[A]. Given: Rate=1.5×102 mol L1 min1\text{Rate} = 1.5 \times 10^{-2} \text{ mol L}^{-1} \text{ min}^{-1} Concentration [A]=0.5 M[A] = 0.5 \text{ M}

First, we calculate the rate constant (kk): k=Rate[A]=1.5×1020.5=3.0×102 min1k = \frac{\text{Rate}}{[A]} = \frac{1.5 \times 10^{-2}}{0.5} = 3.0 \times 10^{-2} \text{ min}^{-1}

The half-life (t1/2t_{1/2}) of a first-order reaction is related to the rate constant by the formula: t1/2=0.693kt_{1/2} = \frac{0.693}{k}

Substituting the value of kk: t1/2=0.6933.0×102=23.1 mint_{1/2} = \frac{0.693}{3.0 \times 10^{-2}} = 23.1 \text{ min}.

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