Worksheet: Carbon Dating

In this worksheet, we will practice calculating the age of objects based on their activity per kilogram due to carbon-14.

Q1:

By what decay process does carbon-14 decay into nitrogen?

  • AGamma emission
  • BNeutron emission
  • CAlpha decay
  • DBeta decay
  • ENeutron capture

Q2:

Which of the following formulas correctly shows the decay of carbon-14 into nitrogen-14?

  • A 1 4 6 1 4 7 โ€“ C N + e + ฬ„ ๐œˆ ๏Œพ
  • B 1 4 6 1 4 6 โ€“ C N + e + ฬ„ ๐œˆ ๏Œพ
  • C 1 4 6 1 3 7 + C N + e + ๐œˆ ๏Œพ
  • D 1 4 6 1 5 7 โ€“ C N + e + ฬ„ ๐œˆ ๏Œพ
  • E 1 4 6 1 4 7 + C N + e + ฬ„ ๐œˆ ๏Œพ

Q3:

Which of the following statements correctly explains why it is not possible to use carbon dating to determine the age of an object that is more than 100,000 years old?

  • A 100,000 years ago, a large meteor strike changed the ratio of 1 4 2 C O to 1 2 2 C O in the atmosphere; thus, measurements of carbon-14 in objects older than 100,000 years are unreliable.
  • BAfter 100,000 years, the proportion of carbon-14 that is left in an object is less than 0.001% of the carbon-14 that was originally in the object. This produces count rates that are too low for most detectors to measure.
  • C 100,000 years ago, carbon-14 was not being produced in Earthโ€™s atmosphere; therefore, none of the organisms that were living 100,000 years ago contained any carbon-14.
  • D 100,000 years ago, a large volcanic eruption changed the ratio of 1 4 2 C O to 1 2 2 C O in the atmosphere; thus, measurements of carbon-14 in objects older than 100,000 years are unreliable.

Q4:

Carbon-14 has a half-life of 5,730 years. How long does it take for an amount of carbon-14 in a sample of a material to reduce to 0.1% of its initial value? Give your answer to 3 significant figures.

Q5:

The following nuclear equation shows how carbon-14 is produced in Earthโ€™s upper atmosphere.

1 4 7 1 0 1 4 6 1 1 X + n C + p

What is the element marked by X?

  • ACarbon
  • BOxygen
  • CNeon
  • DNitrogen
  • EBoron

Q6:

The proportion of carbon-14 in a living organism remains roughly constant over time, even though carbon-14 undergoes radioactive decay to nitrogen. Which of the following statements correctly explains why this is the case?

  • ACarbon-14 is constantly being produced through radioactive decay processes within living organisms and is thus constantly being replenished.
  • BCarbon-14 has a half-life greater than 1,000,000 years. Most organisms live for less than 100 years, so the amount of carbon-14 that decays in this time period is very small.
  • CCarbon-14 binds more strongly to other elements than carbon-12, so once it forms chemical bonds in a living organism, it persists within the organism for longer.
  • DCarbon-14 is continually being produced in the upper atmosphere, and it combines with oxygen to form carbon dioxide. This carbon dioxide is absorbed by plants, which are in turn eaten by animals, thus constantly replenishing the carbon-14 in an organism.

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