Nuclear Equations and Half-Life Problems

Which statement explains why nuclear waste

materials may pose a problem?

• They frequently have short half-lives and remain radioactive for brief periods of time.

• They frequently have short half-lives and remain radioactive for extended periods of time.

• They frequently have long half-lives and remain radioactive for brief periods of time.

• They frequently have long half-lives and remain radioactive for extended periods of time.

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NGSS.HS-PS1-8

After 32 days, 5 milligrams of an 80-milligram sample of a radioactive isotope remains unchanged. What is the half-life of this element?

• 8 days

• 2 days

• 16 days

• 4 days

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NGSS.HS-PS1-8

Which radioisotope undergoes beta decay and has a half-life of less than 1 minute?

• Fr-220

• N-16

• K-42

• P-32

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NGSS.HS-PS1-8

What is the half-life and decay mode of Rn-222?

• 1.91 days and alpha decay

• 1.91 days and beta decay

• 3.82 days and alpha decay

• 3.82 days and beta decay

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NGSS.HS-PS1-8

What is the half-life of sodium-25 if 1.00 gram of a 16.00 gram sample of sodium-25 remains unchanged after 237 seconds?

• 47.4 s

• 59.3 s

• 79.0 s

• 118 s

If 1/8 of an original sample of krypton-74 remains unchanged after 34.5 minutes, what is the half-life of krypton-74?

• 11.5 min

• 23.0 min

• 34.5 min

• 46.0 min

An original sample of K-40 has a mass of 25.00 grams. After 3.9 × 10⁹ years, 3.125 grams of the original sample remains unchanged. What is the half-life of K-40?

• 1.3 × 10⁹ y

• 2.6 × 10⁹ y

• 3.9 × 10⁹ y

• 1.2 × 10¹⁰ y

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NGSS.HS-PS1-8

An original sample of the radioisotope fluorine-21 had a mass of 80.0 milligrams. Only 20.0 milligrams of this original sample remain unchanged after 8.32 seconds. What is the

half-life of fluorine-21?

• 1.04 s

• 2.08 s

• 4.16 s

• 8.32 s

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NGSS.HS-PS1-8

After decaying for 48 hours, 1/16 of the original mass of a radioisotope sample remains unchanged. What is the half-life of this radioisotope?

• 3.0 h

• 9.6 h

• 12 h

• 24 h

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NGSS.HS-PS1-8

Given the nuclear equation:

Which particle is represented by X?

• alpha

• beta

• neutron

• positron

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NGSS.HS-PS1-8