Nuclear Reactions and Half Life

The half life of Thorium-234 is 24 days. What fraction of the element remains after 96 days

• 1/2
• 1/4
• 1/8
• 1/16

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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

What is meant by the statement that ₁₅P³² has a half life of 14 days

• It takes 7 days to go down to 50% radioactivity each time
• It takes 14 days to go down to 50% radioactivity each time
• After 14 days it starts to become less radioactive
• It takes 14 days to go up by 50% radioactivity each time

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NGSS.HS-PS1-8

Which statement is true about half-lives?

• Different atoms of the same nuclide have different half-lives.

• Each radioactive isotope has its own half-life.

• All radioactive nuclides of an element have the same half-life.

• All radioactive nuclides have the same half-life.

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NGSS.HS-PS1-8

What is the half-life of an isotope if 125 g of a 500 g sample of the isotope remain after 3.0 years?

• 1.5 yrs

• 2.5 yrs

• 3.5 yrs

• 4.5 yrs

If you start out with 100 grams of a radioisotope, how much remains after 2 half-lives?

• 100 grams
• 75 grams
• 50 grams
• 25 grams

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NGSS.HS-PS1-8

Gold-198 has a half life of approximately 3 days. If a 100 g sample of gold-198 decays for 9 days, approximately how much gold-198 remains?

• 13g

• 25g

• 33g

• 50g

The half-life of phosphorus-32 is 14.30 days. How many milligrams of a 20.00 mg sample of phosphorus-32 will remain after 85.80 days?

• 3.333 mg

• 0.6250 mg

• 0.3125 mg

• 0.1563 mg

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NGSS.HS-PS1-8

A 100-gram sample of radium-226 has a half-life of 1,600 years. How long will it take before there are only 12.5 grams of the radioactive radium-226 remaining?

• 1,600 years

• 3,200 years

• 4,800 years

• 6,400 years

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NGSS.HS-PS1-8

A rock sample contains 80 g of a potassium-40 isotope with a half-life of 1.25 billion years. How much of the potassium-40 isotope will remain after 2.5 billion years have passed?

• 0 g

• 10 g

• 20 g

• 80 g

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NGSS.HS-PS1-8