Half-Life Calculations-More Practice

Which diagram best represents the percentage of this radioactive isotope sample that will remain after 2 half-lives?

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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

The half-life of Zn-71 is 2.4 minutes. If 6.25 g of Zn-71 are needed for an experiment, how much should be prepared if it will take 9.6 minutes before the experiment can begin?

^{(i.e. you need the START amount)}

• 100.0g

• 50.0g

• 12.5g

• 8.5g

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NGSS.HS-PS1-8

Barium-122 has a half-life of 2 minutes. If after 10 minutes a sample of 15.0 g is left, what mass must have been initially present?

• 30 g

• 480 g

• 240 g

• 120 g

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NGSS.HS-PS1-8

The half-life of Po-218 is three minutes. If it is allowed to decay from 150.0 grams to 2.34 grams, how many half lifes have occured?

• 6 half lifes

• 3 half lifes

• 8 half lifes

• 5 half lifes

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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? Round to two decimal points.

(a)  

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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

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

A radioisotope of silver has half life of 10 minutes. What fraction of the original mass would remain after one hour?

• 1/64
• 1/2
• 1/4
• 1/8

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NGSS.HS-PS1-8

Selenium-83 has a half life of 25 minutes. How many minutes would it take for a 20 milligram sample to decay and only have 1.25 milligrams of it remaining? 

• 25 minutes
• 50 minutes
• 75 minutes 
• 100 minutes

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NGSS.HS-PS1-8