Question

A first order reaction takes 20 minutes for 25 decomposition the time when 75% of the reaction will be completed

Answer 1

The time required for the 75% of reaction will be completed will be 92.3min

Answer 2

k = 2.303/20 min log(100/100-25)

calculate this for the value of k

and we know that t= 2.303/k log(2.303 /100- 25 )

put the value of k in above equation...and plzz keep this in mind that in above 25 is the concentration of reactant which havnt reacted yet means 100-75=25 frm here i got this value