Half-life Practice

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? SHOW WORK

• 100.0g
• 50.0g
• 12.5g
• 8.5g

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

Tags

NGSS.HS-PS1-8

 Fermium-253 has a half-life of 0.334 seconds. A radioactive sample is considered to be completely decayed after 10 half-lives. How much time will elapse for this sample to be considered gone? SHOW WORK

• 0.334 seconds
• 3.34 seconds
• 1.77 seconds
• 13.4 seconds

Tags

NGSS.HS-PS1-8

The half life of iodine-131 is 8.040 days. What percentage of an iodine-131 sample will remain after 40.20 days? SHOW WORK

• 312.5%
• 31.25%
• .3125%
• 3.125%

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? SHOW WORK

• 0.25g
• 2.5g
• 25g
• 80g

The half-life of strontium-90 is 25 years. How much strontium-90 will remain after 125 years if the initial amount is 4.0 g? SHOW WORK

• 3.0g
• 0.125 g

• 0.3g
• 0.25g

Tags

NGSS.HS-PS1-8

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? SHOW WORK

• 1 half-life
• 2 half-lives
• 3 half-lives
• 4 half-lives

Tags

NGSS.HS-PS1-8

If 20 g of copper-64 has a half-life of 13 hours, what mass of copper-64 will remain after 39 hours? SHOW WORK ( Drag the answer to the space.)​ ​ (a)  

• 2.5 g
• 20 g
• 10 g
• 1.25 g
• 5 g
• 0.625

Tags

NGSS.HS-PS1-8

If one-fourth of the carbon-14 is remaining then how many half-lives have passed?

• 1
• 2
• 3
• 4

Tags

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?  SHOW WORK

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