Half-Life Practice

Front

What is half-life?

Back

Half-life is the time required for half of the radioactive atoms in a sample to decay.

Front

How do you calculate the remaining mass after a certain number of half-lives?

Back

Remaining mass = Initial mass × (1/2)^(number of half-lives)

Front

If a sample has a half-life of 10 days, how much of a 40 g sample remains after 30 days?

Back

5 g remains after 30 days (3 half-lives: 40g -> 20g -> 10g -> 5g).

Front

What is the formula to find the number of half-lives that have passed?

Back

Number of half-lives = Total time elapsed / Half-life duration.

Front

If a radioisotope has a half-life of 5 hours, how much of a 16 g sample remains after 15 hours?

Back

2 g remains after 15 hours (3 half-lives: 16g -> 8g -> 4g -> 2g).

Front

What is the relationship between half-life and decay constant?

Back

Decay constant (λ) = ln(2) / half-life.

Front

How do you determine the half-life from a decay graph?

Back

Identify the time it takes for the substance to reduce to half its initial amount.

Front

What mass of a 12 g sample remains after 2 half-lives?

Back

3 g remains after 2 half-lives (12g -> 6g -> 3g).

Front

If a substance decays from 80 g to 10 g, how many half-lives have passed?

Back

4 half-lives have passed (80g -> 40g -> 20g -> 10g).

Front

What is the half-life of a substance if 25% remains after 3 hours?

Back

The half-life is 1 hour (3 half-lives: 100% -> 50% -> 25%).