Question

For a given reaction of first order, it takes $20$ minutes for the concentration to drop from $1.0$ $M$ to $0.6$ $M$. The time required for the concentration to drop from $0.6$ $M$ to $0.36$ $M$ will be:

• A. more than $20$ minutes
• B. less than $20$ minutes
• C. equal to $20$ minutes
• D. infinite time

Answer 1

Answer: (C)

equal to $20$ minutes

$k=\frac{\ln \left(\frac{1.0}{0.6}\right)}{20}{min}^{-1}=0.02554{min}^{-1}$

For $A=0.36$ and $A_o=0.6$ we have,

$t=\frac{\ln \left(\frac{0.6}{0.36}\right)}{0.02554}=20minutes$