Question

The half-life of a radioactive isotope is the time it takes for a quantity of the isotope to be reduced to half its initial mass. Starting with 180 grams of a

radioactive isotope, how much will be left after 4 half-lives?
Use the calculator provided and round your answer to the nearest gram.
grams
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5

Answer 1

According to the definition of half-life, the mass of the radioactive isotope halfs its mass after each half-life, which means the remaining mass is always half the amount of the previous mass.

Therefore, after the 1st half-life, there is (190/2) g left; after the 2nd half-life, there is (190/2)/2 g left; so on and so forth. After the 6th half-life, there is 190/(2*2*2*2*2*2) g = 190g/64 = 2.97 g left.

So 2.97 g of this radioactive isotope will be left after 6 half-lives.

Step-by-step explanation: