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A first order reaction has a specific reaction rate of $10^{-2}\ s^{-1}$. How much time will it take for 20 g of the reactant to reduce to 5 g?
Explanation
20 g → 5 g is two half-lives.
Detailed Solution
$t_{1/2} = \frac{0.693}{10^{-2}}$ second
For reduction of 20 g of reactant to 5 g, two $t_{1/2}$ are required.
$t = 2\times\frac{0.693}{10^{-2}}$ second = 138.6 second