Radioactive Decay and Half-Life Quiz

The half-life of an isotope is 10 days. What percent of this isotope would be left after 50 days?

• 6.25%

• 12.5%

• 1.5625%

• 3.125%

How many milligrams would be left of an original 300 mg sample after 80 minutes if the half-life is 20 min?

• 9.35 mg

• 18.75 mg

• 37.5 mg

• 3.125 mg

The half-life of an isotope is 5 minutes. How long would it take for 400 g of this isotope reduced to 25 g?

• 40 min

• 80 min

• 20 min

• 10 min

An isotope has a half-life of 100 hours. If you start with 40 grams, how many hours would it take until the isotope was reduced to 2.50 grams?

• 400 hrs

• 200 hrs

• 600 hrs

• 100 hrs

After 60 hours, only 3.125% of an original sample remained undecayed. How many half-lives have passed?

• 3

• 5

• 4

• 6

A 300 g sample of a sodium isotope decays to 18.75 g within 200 hrs. What is the half-life of this radioactive isotope of sodium?

• 30 hrs

• 60 hrs

• 40 hrs

• 50 hrs

What is the half-life of a 100.0 g sample of an isotope that decays to 6.25 g in 80 seconds?

• 75 sec

• 30 sec

• 40 sec

• 20 sec

A particular isotope has a half-life of 20 years. How many years will it take for 650 g of it to decay to a 40.625 g sample?

• 80 yrs

• 60 yrs

• 50 yrs

• 30 yrs

An isotope has a short half-life of 15 hrs. How long will it take 475 g of this isotope to decay to 29.6875 g?

• 60 hrs

• 80 hrs

• 50 hrs

• 40 hrs

Put the above different types of radiation in order from most penetrating to least penetrating.

• Alpha>Beta>Gamma

• Gamma>Alpha>Beta

• Gamma>Beta>Alpha

• Beta>Gamma>Alpha