For the reaction 2A+B→3C+D Rate constant of first – order reaction k=
2.303
t
log10
(A)0
(A)t
or k=
2.303
1
×log10
0.8
0.1
....(i) (because 0.6 mole of-0.225 B is formed)Suppose t1 hour is required for changing the concentration of A from 0.9 mole to 0.675 mole of B. Remaining mole of A=0.9 −0.675−0.225 ∴k=