half life

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

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

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

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

What is the half-life of iodine-131?

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

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

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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

Geologist use the time it takes for a radioactive isotope to decay to half its original mass called a___________.

• radioactive decay

• isotope

• half-life

• carbon dating

If the half-life of uranium-232 is 70 years, how long will it take for a 10.0 g sample to be reduced to 0.625 g?

• 232 years

• 17.5 years

• 140 years

• 280 years

Selenium-83 has a half life of 25 minutes. A sample of Selenium-83 is placed in a sealed container. After 100 minutes, the container is opened and 1.25 mg of Selenium-83 are removed. How much Selenium-83 was in the original sample?

• 5.0 mg

• 100. mg

• 83 mg

• 20.0 mg