The thermal decompoistion of compound is of first order. If `50%` of a sample of the compound is decompoistion in `120 min` how long will it take for `90%` of the compound to decompose?

Options

A. `399 min`
B. `410 min`
C. `250 min`
D. `120 min`

Answer

A

Explanation

`k = (0.6932)/(120)` …(i)
`k = (2.303)/(t) log. (a)/(0.10 a)`
`= (2.303)/(t)log 10` …(ii)
Equating (i) and (ii),
`(0.6932)/(120) = (2.303)/(t)`
`t = 399 min`