Radioactive Decay and Half-Lives

The video tutorial covers solving half-life problems for various elements, including radon, caesium-137, carbon-14, germanium-66, strontium-90, and uranium-235. It explains how to calculate the remaining mass or age of a sample by understanding the concept of half-life and applying it to different scenarios. The tutorial emphasizes working backwards and sketching out the problem rather than relying on formulas.

If radon has a half-life of 0.38 days, how many times does it halve in 7.6 days?

• Four times

• Once

• Twice

• Three times

What was the original mass of the radon sample if 6 grams remain after 7.6 days?

• 18 grams

• 12 grams

• 6 grams

• 24 grams

How much of a 100-gram sample of caesium-137 remains after 128 years?

• 12.5 grams

• 50 grams

• 6.25 grams

• 25 grams

How many half-lives have passed for a caesium-137 sample in 128 years?

• 4

• 3

• 5

• 2

What is the age of a fossilized sample if it originally contained 96 kg of carbon-14 and now contains 3 kg?

• 28,650 years

• 34,380 years

• 11,460 years

• 17,190 years

How many times has the carbon-14 sample halved if it now contains 3 kg?

• 3 times

• 5 times

• 6 times

• 4 times

What is the half-life of germanium-66 if a 48-gram sample reduces to 3 grams in 10 hours?

• 4.5 hours

• 3.5 hours

• 2.5 hours

• 1.5 hours

How long will it take for 1 gram of strontium-90 to decay to 250 milligrams?

• 86.4 years

• 57.6 years

• 115.2 years

• 28.8 years

How many billion years will it take for uranium-235 to decay from 600 kg to 7.5 kg?

• 2.8 billion years

• 2.1 billion years

• 1.4 billion years

• 0.7 billion years

How many times does uranium-235 halve to reach 7.5 kg from 600 kg?

• 3 times

• 4 times

• 5 times

• 6 times