Question

A sample initially contains 4.4 moles of a radioactive isotope. How much of the sample remains after four half-lives?

Answer 1

Answer:

0.275

Explanation:

Given that:

Initial number of miles of radioactive isotope = 4.4 moles

How much if the sample remains after 4 half life's

Half-life refers to the time taken by a sample to reduce to half of it's initial value.

After the first half life :

Initial / 2 = 4.4 / 2 = 2.2 moles

Second half life :

2.2 / 2 = 1.1 moles

Third half life :

1.1 / 2 = 0.55 Moles

Fourth half life :

0.55 / 2 = 0.275 moles