Question

Concentration of the reactant in first-order is reduced to $\frac{1}{e^{2}}$after : (Natural life = $\frac{1}{K}$ )

• A. One natural life-time
• B. Two-natural life-time
• C. Three natural life-time
• D. Four natural life-time

Answer 1

Answer: (B)

Two-natural life-time

Answer 2

$C_{t} = C_{0}e^{- Kt}$

$\frac{1}{e^{2}} \times C_{0} = C_{0} = e^{- Kt}$

$e^{- 2} = e^{- Kt}$

$t = \frac{2}{K}$

t = 2 natural life time.