Half-Lives

The half-life of Zn-71 is 2.4 minutes. If one had 100.0 g at the beginning, how many grams would be left after 7.2 minutes has elapsed?

• 100.0g

• 50.0g

• 12.5g

• 8.5g

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NGSS.HS-PS1-8

Which of the following statements is true?

• An unstable daughter isotope decays into a stable parent isotope.

• An unstable parent isotope decays into a stable daughter isotope.

• A stable daughter isotope decays into an unstable parent isotope.

• A stable parent isotope decays into an unstable daughter isotope.

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NGSS.HS-PS1-8

Barium-122 has a half-life of 2 minutes. A fresh sample weighing 80 g was obtained. If it takes 10 minutes to set up an experiment using barium-122, how much barium-122 will be left when the experiment begins?

• 0.25g

• 2.5g

• 25g

• 80g

¹⁴₆C has a half life of 5730 years, how many years would it take the 4.0 g sample to decay to 0.25 g?

• 4 years

• 5730 years

• 22,920 years

• 28,650 years

A 2.5 gram sample of an isotope of strontium-90 was formed in a 1960 explosion of an atomic bomb at Johnson Island in the Pacific Test Site. The half-life of strontium-90 is 28 years. In what year will only 0.625 grams of this strontium-90 remain?

• 1988

• 2016

• 2044

• 2072

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NGSS.HS-PS1-8

The half life of iodine-131 is 8 days. What fraction of an iodine-131 sample will remain after 40 days?

• 1/2

• 1/64

• 1/5

• 1/32

Tags

NGSS.HS-PS1-8

What is the definition of half-life?

• Time it takes for half of the atoms in a radioactive substance to decay.

• Time it takes for half of the atoms in a radioactive substance to combine.

• Time it takes for all of the atoms in a radioactive substance to decay.

• Time it takes for half of the atoms in a non-radioactive substance to decay.

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NGSS.HS-PS1-8

A radioactive substance has a half-life of 10 years. If you start with 100 grams of the substance, how much will remain after 30 years?

• 25 grams

• 12.5 grams

• 50 grams

• 75 grams

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NGSS.HS-PS1-8

A radioactive substance has a half-life of 2 hours. If you start with 500 grams of the substance, how much will remain after 6 hours?

• 125 grams

• 250 grams

• 375 grams

• 62.5 grams

Tags

NGSS.HS-PS1-8

The half-life of a radioactive isotope is 1 year. If you start with 1000 grams of the isotope, how much will remain after 3 years?

• 125 grams

• 250 grams

• 500 grams

• 750 grams

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NGSS.HS-PS1-8