Calculating Half-life

You have 100 grams of radioactive C-14. The half life of C-14 is 5730 years. 
How many grams are left after 1 half life? 

• 100 grams
• 25 grams
• 2 grams
• 50 grams

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NGSS.HS-PS1-8

After the third half-life, how much of the sample is left?

• 1/2
• 1/3
• 1/16
• 1/8

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NGSS.HS-PS1-8

If 10 mg of iodine 131 is given to a patient, how much is left after 24 days? The half-life of iodine-131 is 8 days.

• 1.25mg
• 1.25g
• 10g
• 10mg

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NGSS.HS-PS1-8

The half-life of strontium-90 is 25 years. How much strontium-90 will remain after 100 years if the initial amount is 4.0 g?

• 3.0g
• 0.25mg
• 0.3g
• 0.25g

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NGSS.HS-PS1-8

If the half-life of uranium-232 is 70 years, how many half-lives will it take for 10 g of it to be reduced to 1.25 g?

• 1 half-life
• 2 half-lives
• 3 half-lives
• 4 half-lives

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NGSS.HS-PS1-8

After 22,800 years, approximately what percentage of the original carbon-14 remains?

• 15%

• 12.5%

• 6.25%

• 3.125%

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NGSS.HS-PS1-8

What is the half-life of iodine-131?

• 32 days
• 8 days
• 16 days
• 24 days

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NGSS.HS-PS1-8

The % of the parent isotope remaining after 1 Half Life.

• 50%

• 25%

• 12.5%

• 6.25%

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NGSS.HS-PS1-8

What is the Half life of this isotope?

• 5 seconds

• 10 seconds

• 15 seconds

• 20 seconds

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NGSS.HS-PS1-8

What is the Half Life of this isotope?

• 3 days

• 5 days

• 8 days

• 10 days

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NGSS.HS-PS1-8