MCQ
The rate constant for a first order reaction is $20\,min ^{-1}$. The time required for the initial concentration of the reactant to reduce to its $\frac{1}{32}$ level is $........\times 10^{-2}\,min$. (Nearest integer)(Given: $\quad \ln 10=2.303, \log 2=0.3010)$
  • A
    $16$
  • B
    $15$
  • $17$
  • D
    $14$

Answer

Correct option: C.
$17$
c
$C=\frac{C_o}{2^n}=\frac{C_o}{32}$

$n =5$

$t =5 t _{1 / 2}$

$=\frac{5 \times 0.693}{20}=\frac{0.693}{4}$

$=0.17325\,min =17.325 \times 10^{-2}\,min$

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