After three half- lives, a sample contains 10 grams of parent isotopes. How many grams of the parent isotope were present to start?

its not for biology..... its for Earth/Space Science

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throwdolbeau throwdolbeau · Answer 1 · 2019-08-13T07:25:48+02:00

Answer: Initial amount of parent isotope present in the sample was 80 grams.

Explanation: Initial amount was= 80 grams

The sample undergone radioactive decay and after first half-life, it has= 40 grams (half of initial amount)

after second half-life, it has= 20 grams

And after third half-life, it has= 10 grams

Thus, the sample at present has 10 grams and initially had 80 grams of the parent isotope materials.

marcos3men2 marcos3men2 · Answer 2 · 2021-10-01T21:34:36+02:00

Answer:

The answer is 80

Explanation:

a half lives takes away half of an amount, in the question it said 3 half- lives.

the only posible answer is 80.

FIRST half lives: 80-40=40

SECOND half lives: 40-20=20

THIRD half lives: 20-10=10

80 is the only way to get to 10 with three half-lives.

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