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Juliet started working with a radioactive substance. In 1997, she started with 200 g. When she measured again in 2002, she had 100 g left. In 2007, she had 50 g. Which substance is she most likely measuring?

Arubidium-91
Biodine-131
Ccobalt-60
Dcarbon-14

Verified Answer :

MissPhiladelphia

Cobalt-60, 60Co
, is a synthetic radioactive isotope of
cobalt with a half-life of 5.2714 years. It
is produced artificially in nuclear
reactors. Deliberate industrial production depends on neutron
activation of bulk samples of
the monoisotopic and mononuclidiccobalt isotope 59Co

Answer: C. cobalt-60

Explanation:

Given: The sample remains half of its original sample after 5 years (2002-1997)=5 years.

The radioactive isotope rubidium-91 used for radiotherapy has a half-life of 58.4 seconds. A sample originally containing 200 g of rubidium-91 would contain only 100 g of rubidium-91 after 58.4 seconds.

The radioactive isotope iodine-131 used for radiotherapy has a half-life of 8.02 days. A sample originally containing 200 g of iodine-131  would contain only 100 g of iodine-131  after 8.02 days.

The radioactive isotope cobalt-60, used for radiotherapy has a half-life of 5.26 years. A sample originally containing 200 g of cobalt-60 would contain only 100 g of cobalt-60 after 5.26 years.

The radioactive isotope carbon-14, used for radiotherapy has a half-life of 5,730 years. A sample originally containing 200 g of carbon-14 would contain only 100 g of carbon-14 after 5,730 years.

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