Half-Life Practice

Front

What is half-life?

Back

The time required for half of the radioactive atoms in a sample to decay.

Front

How do you calculate the number of half-lives?

Back

Divide the initial mass by the final mass and then take the logarithm base 2 of that number.

Front

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

Back

5 g.

Front

What happens to the mass of a radioisotope after each half-life?

Back

It is reduced by half.

Front

If 80 g of a radioisotope remains after 2 half-lives, what was the original mass?

Back

320 g.

Front

What is the half-life of a substance if 25% of the original sample remains?

Back

It has undergone 2 half-lives.

Front

How many half-lives are needed for a 16 g sample to decay to 1 g?

Back

4 half-lives.

Front

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

Back

The decay constant (λ) is inversely proportional to the half-life (t1/2): λ = ln(2) / t1/2.

Front

If a radioisotope has a half-life of 5 years, how much of a 10 g sample remains after 15 years?

Back

1.25 g.

Front

What is the significance of a constant half-life in radioactive decay?

Back

It indicates that the rate of decay does not change over time.