Half-Life

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

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

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

Which type of nuclear radiation is being emitted here?

• Alpha

• beta

• gamma

• none

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NGSS.HS-PS1-8

You have 100 grams of radioactive C-14. The half life of C-14 is 5715 years. 
How many grams are left after each half life? 

• 6.25g or 1/16

• 3 half lives

• 25g or 1/4

• 2 half lives

• 50g or 1/2

• 4 half lives

• 12.5g or 1/8

• 1 half life

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NGSS.HS-PS1-8

An isotope of cesium 138 has a half-life of 30 years. If 1.00 g of cesium-138 disintegrates over a period of 90 years, how many grams of cesium-138 would remain?

Mathematical Equivalence

ON

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NGSS.HS-PS1-8

Ge-81 emits beta particles and has a half-life of 7.6 seconds.

Determine the time required for a 16.00-gram sample of Ge-81 to decay until only 1.00 gram of the sample remains unchanged.

• 1/8 radioactive

• 4 grams

• 1/4 radioactive

• 8 grams

• 1/2 radioactive

• 16 grams

• 1/16 radioactive

• 2 grams

• Completely radioactive

• 1 grams

If 20 g of copper-64 has a half-life of 13 hours, what mass of copper-64 will remain after 39 hours? ( Drag the answer to the space.)​ ​ (a)  

• 2.5 g

• 20 g

• 10 g

• 1.25 g

• 5 g

• 0.625

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NGSS.HS-PS1-8

A radioactive isotope has a half-life of 2.5 years. Match the correct fraction of the original mass that remains unchanged after the given amount of years

• 1/4 radioactive

• 5 years

• 1/32 radioactive

• 7.5 years

• 1/16 radioactive

• 12.5 years

• 1/8 radioactive

• 10 years

• 1/2 radioactive

• 2.5 years

When an isotope goes through 4 half-lives, _____ _________________ remains

• 1/4 or 25%

• 1/8 or 12.5%

• 1/16 or 6.25%

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NGSS.HS-PS1-8