A chemical reaction of the general type
A-2B
is first-order. with a rate constant of
1.52x10-4s-1.

A. Calculate the half-life of A.
B.Assuming the initial concentration of A is 0.067mol L-1, calculate the time needed for the concentration to fall to 0.010mol L-1.

Question

A chemical reaction of the general type
A->2B
is first-order. with a rate constant of
1.52x10-4s-1.

A. Calculate the half-life of A.
B.Assuming the initial concentration of A is 0.067mol L-1, calculate the time needed for the concentration to fall to 0.010mol L-1.

cuanchi · Answer

A. 
the half life for a first order reaction is independent of the initial concentration of A and respond at the formula 
t1/2= 0.693/k
k= rate constant

B.
use the integrated equation for the first order reaction 
ln [A]f = -k t + ln [A]o
isolate t = time 
has to be ~ 2.5 half-lifes