Question

43. We have a radioactive isotope called RI which has a half-life of 12 million years. A geologist

has used radiometric dating and determined the rock to be approximately 36 million years old
How many half lives have taken place?
(1 point)
OOOO

Answer 1

Answer: Thus 3 half lives have taken place.

Step-by-step explanation:

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

`t=(2.303)/(k)\log(a)/(a-x)`

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.

`t_{(1)/(2)}=(2.303)/(k)\log(100)/(50)`

`t_{(1)/(2)}=(0.693)/(k)`

Number of half lives =
`\frac{\text {total time}}{\text {half life}}=(36million)/(12million)=3`

Thus 3 half lives have taken place.