Answer: 360 minutes are required for 20 percent of a sample of cyclopropane to isomerize topropane.
Step-by-step explanation:
Half life is the amount of time taken by a radioactive material to decay to half of its original value.
As the units of rate constant is
, the reaction follows first order kinetics.
Expression for rate law for first order kinetics is given by:
where,
k = rate constant =

t = time for decomposition = ?
a = let initial amount of the reactant = 100
x = amount decayed =

a - x = amount left after decay process = 100-20= 80
Thus 360 minutes are requiredfor 20 percent of a sample of cyclopropane to isomerize topropane.