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18.Calcium-49, a radioactive isotope, has a half-life of 9 minutes. If an 80-gram sample of the isotope decays for 27 minutes, how many grams of the original sample remain?Select one:a. 60b. 10c. 40d. 20

User Fire Fist
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1 Answer

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Step-by-step explanation:

The half-life period is represented by the abbreviation P. The time that a material has suffered disintegration is represented by t. Thus, if we know the half-life and the disintegration time (represented by x), we can say how many half-lives a material has gone through until a certain moment. This is done through the relationship below:

t = x * P

With this knowledge, we can still determine the mass that remains after the half-life period from the expression:

m = mo/2^x

were m = mass left

mo = initial mass

x = half-life

Here we have:

P = 9 minutes

t = 27 minutes

x = ????

mo = 80 g

So first let's find x:

t = x*P

27 = x*9

x = 3

now let's find m:

m = mo/2^x

m = 80/2^3

m = 80/8

m = 10 g

Answer: b. 10

User PearsonArtPhoto
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