t75% = 2t50%
t50% = (t75% /
2) = (60/2) = 30 min
In 140 days ⟹ initial concentration
reduced to (1/2)g
In 280 days ⟹ initial concentration
reduced to (1/4)g
In 420 days ⟹
initial concentration reduced to (1/8)g
In 560 days ⟹ initial concentration
reduced to (1/16)g
For a first order
reaction
t1/2 =
0.6932/k
For a second order
reaction
4t1/2 = 2
hours
t1/2 = 30 min