Half Life Decay

If 10 mg of iodine 131 is given to a patient, how much is left after 24 days? The half-life of iodine-131 is 8 days.

• 25mg

• 1.25g

• 10g

• 10mg

After the third half-life, how much of the sample is left?

• 1/2

• 1/3

• 1/16

• 1/8

Tags

NGSS.HS-PS1-8

If the half-life of uranium-232 is 70 years, how many half-lives will it take for 10 g of it to be reduced to 1.25 g?

• half-life

• half-lives

• half-lives

• half-lives

Tags

NGSS.HS-PS1-8

What is the half-life of iodine-131?

• 32 days

• 8 days

• 16 days

• 24 days

Tags

NGSS.HS-PS1-8

The time it takes for half of the atoms in a radioactive element to decay.

• Half Life

• Fossils

• Relative Dating

• Absolute Dating

Tags

NGSS.HS-PS1-8

The half-life of a radioactive substance is the amount of time it takes for _____ of the parent atom to decay.

• 1/4

• 1/2

• 3/4

• all

Tags

NGSS.HS-PS1-8

The half-life of C-14 is 5470 years. If a fossil has one-quarter of its original radioactivity remaining, what is the best estimate for its age?

• 5470 years

• 10940 years

• 16410 years

• 300 years

Answer explanation

This fossil would be 5470 years old if half of C-14 remained. Since 1/4th of the C-14 remains, you have to multiply 5470 by 2. The total number of years is 10940.

5470 x 2 = 10940

Tags

NGSS.HS-PS1-8

What percentage of rubidium-87 atoms will be left after four half lives?

• 25.0%

• 12.5%

• 6.25%

• 3.125%

Tags

NGSS.HS-PS1-8

A sample of granite is analyzed using the

K-40 --> Ar-40 method.

Of the original 1200 grams of potassium

only 75 grams remain.

How many half lives has this granite been through?

Tags

NGSS.HS-PS1-8

The half - life of radon - 222 is 3.8 days. How much of a 100 g sample is left after 15.2 days.

• 50.0 g

• 25.0 g

• 12.5 g

• 6.25 g