Question

The initial mass of a radioisotope is 15.0 g. If the radioisotope has a half-life of 2.75 years, how much remains after four half-lives?

Answer 1

0.9375 grams

Step-by-step explanation:

As we know half life is the time period in which quantity of a substance reduces to half of its original value.

The formula to calculate amount of substance left after n half life is
`x/2^n`

where x is the amount of original substance

n is the no of half life.

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Given

No. of half lives = 4

amount of original substance = 15 gram

thus,

n = 4

x = 15 grams

amount of radioisotope left after 4 half life =
`x/2^n = 15 \ gram/2^4 = 15 \ grams / 16 = 0.9375 \ grams\\`

Thus, only 0.9375 grams of radioisotope are left after 4 half lives.