`80%` of a fisrt order reaction was completed in `70 min`. How much it will take for `90%` completion of a reaction?

Options

A. `114 min`
B. `140 min`
C. `100 min`
D. `200 min`

Answer

C

Explanation

`t_(80%) = log.(100)/(100-80) = log.(10)/(2)`
`= log 5 = 0.69 ~~ 0.7`
`t_(90%) = log.(100)/(100-90) = log 10 = 1`
`(t_(80%))/(t_(90%)) = (0.7)/(1) rArr (70)/(t_(90%)) = (0.7)/(1)`
`:. t_(90%) = (70)/(0.7) = (700)/(7) = 100 min`