A first order reaction taken 32 minutes for 50% completion. Hew much time will it take for 90% completion ?

Explanation

Case I : `t_(1//2)`=32 min
`k=(0.693)/(t_(1//2))=(0.693)/("32 min")-0.02165" min"^(-1)`
Case II :
`[R]_0`=100 (say) [R]=100-90=10
k=0.02165 `min^(-1)`,t=?
`t=(2.303)/(k)log([R]_0)/([R])`
`t=(2.303)/(0.02165min^(-1))log(100)/(10)`
`(2.303xxlog10)/(0.02165min^(-1))=(2.303)/(0.02165)` min
=106.37 min