Question

If I now have 3g of Iodine-131, how much did I have 16 days ago?

Answer 1

12 grams of Iodine-13 was present 16 days ago

Step-by-step explanation:

Given:

Amount of Iodine-131 sample present now = 3g

To Find:

Amount of Iodine-131 sample present before 16 days = ?

Solution:

W know that the half life of Iodine-131 is 8days

Let the amount of sample before 16 days be X

Then

The X amount Iodine-131 sample will decay ito ist half after 8 days

after 8 days

=>
`X * (1)/(2)`

=>
`(X)/(2)`

after next 8 days , i.e., 16 days

=>
`(X)/(2)* (1)/(2)`

=>
`(X)/(4)`

Now we know that after 16 days we have 3 grams of Iodine-131 sample

So,

`(X)/(4)` = 3

`X = 4 * 3`

X = 12