Half-life of a reaction
when [D]
=
[D]
0
/2
Zero order
t
1/2
=
[D]
0
/2 k
0
First order
t
1/2
=
( ln 2 ) / k
1
Second order
t
1/2
=
1 / k
2
[D]
0
Shelf-life
t
90
after 10% degradation
First order
t
90
=
( ln 0.9 ) / k
1