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11 June, 09:13

The half-life of radon-222 is 3.8 days. If a sample currently contains 3.1 grams of radon-222, how much radon-222 did this sample have 15.2 days ago?

a 12.4 grams

b 47.1 grams

c 49.6 grams

d 57.8 grams

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Answers (1)
  1. 11 June, 10:45
    0
    The number of grams of radon 222 did it have 15.2 ago was 49.6 grams (answer C)

    calculation

    calculate the number of half life it has covered from 15.2 days to 3.8 days

    that is divide 15.2 / 3.8 = 4 half life

    half life is time taken for a radio activity of a specified isotope to fall to half its original mass

    therefore 3.8 days ago it was 3.1 x2 = 6.2 grams

    7.6 days ago it was 6.2 x2 = 12.4 grams

    11.4 days ago it was 12.4 x2 = 24.8 grams

    15.2 days ago it was 24.8 x2=49.6 grams
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