In this class of reactions, the rate of the reaction is proportional to the
first power of the concentration of the reactant R For example,
R ® P
[
]
[
]
d R
Rate
R
d
k
t
= −
=
or  
[ ]
[ ]
d R
– d
R
k t
=
Integrating this equation, we get
ln [R] = – kt + I
(3 8)
Again, I  is the constant of integration and its value can be determined
easily When  t = 0, R = [R]0, where [R]0 is the initial concentration of the
reactant