Half-Life Review 2024

Carbon-14 has a half-life of 5,730 years. How long will it take for 15 g of a 120.0-g sample to decay radioactively? 5,730 years 11,460 years 17,190 years 22,920 years

17,190 years

A sample originally contained 2.4 g of a radioisotope. It now contains 0.6 g How many half-lives have passed since the sample originally formed? 1 2 3 4

2

Bones are found and they 1/4 Carbon-14 left. How many half lives have past? 1 2 3 4

2 half-lives

Identify the daughter isotope in this nuclear reaction: 222/88 Ra → 218/86 Rn + 4/2 He Which is the daughter isotope? 218/86 Rn 4/2 He 222/88 Ra

218/86 Rn

Identify the parent isotope and daughter isotope in this nuclear reaction: 222/88 Ra → 218/86 Rn + 4/2 He Which is the parent isotope? 218/86 Rn 4/2 He 222/88 Ra

222/88 Ra

A sample contains 6.25 percent parent isotope and 93.75 percent daughter isotopes. If the half-life of the parent isotope is 58 years, how old is the sample?

232 years

A small amount of americium-241 is used in smoke detectors. A stream of radiation flows between two electrodes. If smoke interrupts the stream, the alarm goes off. What feature of the radioisotope americium-241 would be most helpful for the smoke detector to work? long half-life short half-life over-sensitive detection less sensitive detection

long half-life

A sample contains 10.5 g of the radioisotope Pb-212 and 157.5 g of its daughter isotope, Bi-212. How many half-lives have passed since the sample originally formed? 4 14 15 147.5

4

A meteorite contains 0.17 g of nickel-59, a radioisotope that decays to form cobalt-59. The meteorite also contains 5.27 g of cobalt-59. How many nickel-59 half-lives have passed since the meteorite formed? 1 5 5.1 5.44

5

Sodium-24 has a half-life of 15 hours. After 45 hours, how much sodium-24 will remain of an original 50.0-g sample? 5.56 g 6.25 g 16.7 g 25.0 g

6.25 g

An 80.0 g sample of iodine-131 was placed in a sealed vessel forty days ago. Only 2.5 g of this isotope is now left. What is its half-life?(time it started)

8 days

Which radioisotope can scientists use to determine the age of a fossil that is less than 60,000 years old? Uranium-238 Carbon-14

Carbon-14

In radioactive isotopes, ______________________ isotopes, decay into __________ isotopes Stable, unstable Unstable, Stable

In radioactive isotopes unstable isotopes, decay into stable isotopes.

Which definition describes a half-life? The time required for half of a radioactive sample to decay. The time required for half of a radioactive sample to become unstable. The time required for all of a radioactive sample to change because of heat. The time required for all of a sample to break down due to pressure change.

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

The radioisotope that has the longest half-life is the best to use radiocarbon dating 100 million year old rocks. Which radioisotope is the best to use? Uranium-238 Carbon-14

Uranium-238

An article about half-lives describes a parent isotope. What is a parent isotope? the isotope that forms from the radioactive decay of a less stable isotope the isotope that forms from the radioactive decay of a more stable isotope an isotope that undergoes radioactive decay to form a less stable isotope an isotope that undergoes radioactive decay to form a more stable isotope

an isotope that undergoes radioactive decay to form a more stable isotope

Which time frame correctly describes the range of half-lives? fractions of a second to billions of years seconds to minutes minutes to days days to millions of years

fractions of a second to billions of years

Consider the image of a fossil below. How is half-life most likely used with respect to this fossil? to find the mass of the fossil to find the age of the fossil to determine the species shown by the fossil to determine if radiation is being emitted from the fossil

to find the age of the fossil

How much of a sample remains after three half-lives have occurred? 1/16 of the original sample 1/9 of the original sample 1/8 of the original sample 1/3 of the original sample

1/8 of the original sample

Uranium-232 has a half-life of 68.9 years. A sample from 206.7 years ago contains 1.40 g of uranium-232. How much uranium was originally present?

11.2 g