Question

Refer to Figure 13-2 and determine how much parent material will be left after five half-lives

Answer 1

Answer: $3.125g$

Explanation: This is a type of radioactive decay and all the radioactive process follow first order kinetics.

Half life is the time required to decompose half of the reactants. thus after every half life the reactant will decompose to half of its present value.

Now, to calculate the number of half lives, we use the formula:

$a=\frac{a_o}{2^n}$

where,

a = amount of reactant left after n-half lives = ?

$a_o$ =Let Initial amount of the reactant = 100 g

n = number of half lives

$a=\frac{100}{2^5}$

$a=3.125g$

Answer 2

After five half-lives, there will be

           (1/2) · (1/2) · (1/2) · (1/2) · (1/2)  =  1/32  =  3.125%

of the original material remaining.