Half-life

​Half-Life

By Tony Negus

Multiple Choice

What is the half-life of iodine-131?

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

Multiple Choice

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

Multiple Choice

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

Multiple Choice

The diagram shows 32 atoms

32 of the Red are the parent isotope

0 of the atoms are daughter isotopes

How many half-lives have occurred?

• 0

• 1

• 2

• 3

Multiple Choice

What is Half-life?

• The amount of time it takes for some of the nuclei in a sample of the isotope to decay
• The amount of time it takes for half the electrons in a sample of the isotope to decay
• The amount of time it takes for half the nuclei in a sample of the isotope to decay
• the amount of time it takes to double the nuclei in a sample of the isotope to decay

Multiple Choice

The half life of isotope X is 2.0 years. How many years would it take for a 4.0 mg sample of X to decay and have only 0.50 mg of it remain?

• 6.0 years

• 3.0 years

• 8.0 years

• 2.0 years

Multiple Choice

The half-life of Zn-71 is 2.4 minutes. If one had 100.0 g at the beginning, how many grams would be left after 7.2 minutes has elapsed?

• 100.0g
• 50.0g
• 12.5g
• 8.5g

Multiple Choice

After the third half-life, how much of the sample is left?

• 1/2
• 1/3
• 1/16
• 1/8

Multiple Choice

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

Multiple Choice

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

Multiple Choice

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

Multiple Choice

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

Multiple Choice

What is the half-life of iodine-131?

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

Multiple Choice

What is the Half life of this isotope?

• 5 seconds

• 10 seconds

• 15 seconds

• 20 seconds

Multiple Choice

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

Multiple Choice

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

Multiple Choice

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? (FIND M_i)

• 100.0g

• 50.0g

• 12.5g

• 8.5g

Multiple Choice

The half life of isotope X is 2.0 years. How many years would it take for a 4.0 mg sample of X to decay and have only 0.50 mg of it remain?

• 6.0 years

• 3.0 years

• 8.0 years

• 2.0 years

Multiple Choice

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

Multiple Choice

What is the half life for this radioactive isotope?

• 5,700 years

• 11,400 years

• 17,100 years

• 28,500 yeats

Multiple Choice

The half life for a radioactive isotope is 10 years. How many half-lives have passed after 20 years?

• 1 half life

• 2 half lives

• 3 half lives

• 4 half lives

Multiple Choice

You start out with 8 grams of a radioactive isotope. How much radioctive isotope will be left after 2 half lives?

• 8 grams

• 4 grams

• 2 grams

• 1 gram

Multiple Choice

What is the Half Life of this isotope?

• 3 days

• 5 days

• 8 days

• 10 days