The half-life of a first-order reaction is 13 min. If the initial concentration of reactant is 0.085 M, how long would it take until the concentration decreases to 0.055 M

It will take 8.2 minutes until the concentration decreases to 0.055 M

Explanation:

The time after which 99.9% reactions gets completed is 40 minutes

Explanation:

Expression for rate law for first order kinetics is given by:

where,

k = rate constant

t = age of sample

a = let initial amount of the reactant

a - x = amount left after decay process  

a) for completion of half life:

Half life is the amount of time taken by a radioactive material to decay to half of its original value.

b)  Time taken for 0.085 M to decrease to 0.055 M

Thus it will take 8.2 minutes until the concentration decreases to 0.055 M