Half-Life Practice SET2!!

Front

What is half-life?

Back

The half-life of a radioactive substance 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 = Original mass × (1/2)^(number of half-lives).

Front

If a radioisotope has a half-life of 30 minutes, how much will remain after 90 minutes?

Back

After 90 minutes (3 half-lives), 1/8 of the original mass will remain.

Front

What is the half-life of a substance if it takes 120 minutes for its mass to decrease from 6.4 g to 0.4 g?

Back

The half-life is 30 minutes.

Front

If you start with 100 grams of chromium-51, how much will remain after 112 days if its half-life is 28 days?

Back

1600 grams of chromium-51 would have been present originally.

Front

What fraction of a 20.0 gram sample of strontium-90 remains after 75 years if its half-life is 25 years?

Back

1/8 of the original sample remains.

Front

How many half-lives are in 75 years if the half-life is 25 years?

Back

There are 3 half-lives in 75 years.

Front

What is the remaining mass of a 20.0 mg sample of iodine-131 after 24.0 days?

Back

2.50 mg remains after 24.0 days.

Front

If a radioisotope has an original mass of 20.0 g and a half-life of 30 minutes, how long until 2.5 g remains?

Back

It takes 90 minutes for 2.5 g to remain.

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.