The time required for a first order reaction to complete 90% is T. What is the time required to complete 99% of the same reaction?

Options

A. 2t
B. 3t
C. t
D. 4t

Answer

A

Explanation

From the first order reaction, `t=(2.303)/(k)log""(a)/(a-x)`
Here, suppose that a=100
Now putting the values
`t_(90%)=(2.303)/(k)log""((100)/(100-90))`
`t_(99%)=(2.303)/(k)log""((100)/(100-99))`
`(t_(90%))/(t_(99%))=((2.303)/(k)log""((100)/(10)))/((2.303)/(k)log""((100)/(1)))=(1)/(2)`
`t_(99%)=2t`