Question

The half life period of a first order chemical reaction is $6.93$ minutes. The time required for the completion of $99\%$ of the chemical reaction will be ($log\, 2\,=\,0.301$) :

• A. $230.3$ minutes
• B. $23.03$ minutes
• C. $46.06$ minutes
• D. $460.6$ minutes

Answer 1

Answer: (C)

$46.06$ minutes

Answer 2

$\because \lambda=\frac{0.6932}{t_{1/ 2}}=\frac{0.6932}{6.93}min^{-1}$ Also $t=\frac{2.303}{\lambda}log \frac{\left[A_{o}\right]}{\left[A\right]}$ $\left[A_{o}\right]=$ initial concentration (amount) $\left[A\right]=$ final concentration (amount) $\therefore t=\frac{2.303\times6.93}{0.6932}log \frac{100}{1}$ $46.06$ minutes