Radioactive Decay and Half-Life Calculations in Chemistry

The video tutorial explains the concept of half-life through examples of radium, tritium, and thallium decay. It covers calculations of remaining substance amounts over time, using both percentages and fractions. The tutorial also introduces more complex half-life problems involving exponents and logarithms, which will be discussed in a subsequent lesson.

If you start with 120 grams of radium, how much will remain after 44 days?

• 60 grams

• 15 grams

• 30 grams

• 7.5 grams

How many half-lives are equivalent to 44 days if the half-life of radium is 11 days?

• 5 half-lives

• 2 half-lives

• 3 half-lives

• 4 half-lives

What percentage of radium remains after 4 half-lives?

• 50%

• 6.25%

• 25%

• 12.5%

After 4 half-lives, what fraction of radium is left?

• 1/4

• 1/16

• 1/32

• 1/8

How long does it take for an 80 gram sample of tritium to decay to 2.5 grams?

• 24.6 years

• 36.9 years

• 49.2 years

• 61.5 years

What is the half-life of tritium if it takes 61.5 years for an 80 gram sample to decay to 2.5 grams?

• 12.3 years

• 15.4 years

• 18.5 years

• 21.6 years

How many half-lives are needed for tritium to decay from 80 grams to 2.5 grams?

• 3 half-lives

• 4 half-lives

• 5 half-lives

• 6 half-lives

If 200 grams of thallium decays to 12.5 grams in 20 minutes, what is the half-life?

• 7.5 minutes

• 5 minutes

• 10 minutes

• 2.5 minutes

How many half-lives occur when thallium decays from 200 grams to 12.5 grams?

• 3 half-lives

• 2 half-lives

• 5 half-lives

• 4 half-lives

What is the process called when thallium undergoes decay to form lead?

• Alpha decay

• Beta decay

• Gamma decay

• Neutron decay