# Question #f875f

##### 1 Answer

Feb 12, 2017

We know that the equation of rate constant for 1st oder reaction is as follows

#color(blue)(k=1/tln(C_0/C_t)......[1])#

where

For 50% completion of the reaction time is 30 min

so for

So inserting these in [1] we get

#k=1/30ln2......[2]#

Let the reaction becomes 90% complete in

So

The equation [1] then becomes

#k=1/Tln(10).........[3]#

Comparing [2] and [3] we get

#1/30ln2=1/Tln(10)#

#=>T=(30ln10)/ln2~~99.65 min#