Half-Life

Question 1

Which statement is true about radiocarbon dating?

Revolt · Accepted Answer

The half-life of C-14 is 5,730 years.

Question 2

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?

Revolt · Accepted Answer

6.25 g

Question 3

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?

Revolt · Accepted Answer

long half-life

Question 4

A sample originally contained 1.28 g of a radioisotope. It now contains 1.12 g of its daughter isotope. How many half-lives have passed since the sample originally formed?

Revolt · Accepted Answer

3

Question 5

An article about half-lives describes a parent isotope. What is a parent isotope?

Revolt · Accepted Answer

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

Question 6

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?

Revolt · Accepted Answer

4

Question 7

Leutium-176 has a half-life of 3.85 1010 years. After 1.155 1011 years, how much leutium-176 will remain from an original 16.8-g sample?

Revolt · Accepted Answer

2.10 g

Question 8

Carbon-14 has a half-life of 5,730 years. How long will it take for 112.5 g of a 120.0-g sample to decay radioactively?

Revolt · Accepted Answer

22,920 years

Question 9

Niobium-91 has a half-life of 680 years. After 2,040 years, how much niobium-91 will remain from a 300.0-g sample?

Revolt · Accepted Answer

37.5 g

Question 10

Which definition describes a half-life?

Revolt · Accepted Answer

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

Half-Life Answers

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