For a first order reaction A → B the reaction rate at reactant concentration of 0.01 M is found to…

For a first order reaction A $\rightarrow$ B the reaction rate at reactant concentration of 0.01 M is found to be $2.0 \times 10^{-5}$ mole L$^{-1}$ s$^{-1}$. The half life period of the reaction is :-
A 300 s
B 30 s
C 220 s
D 347 s

Detailed Solution

For a first order reaction, rate $= k[A]$
$k = \dfrac{\text{rate}}{[A]} = \dfrac{2.0 \times 10^{-5}}{0.01}$
$k = 2.0 \times 10^{-3}$ s$^{-1}$
Half-life: $t_{1/2} = \dfrac{0.693}{k}$
$t_{1/2} = \dfrac{0.693}{2 \times 10^{-3}}$
$t_{1/2} = 346.5 \approx 347$ s

Half-Life of a First Order Reaction in past papers

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Practise Half-Life of a First Order Reaction All 2 questions This chapter in 2005 AIPMT