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Aliun [14]
3 years ago
11

Scientist can determine the age of ancient objects by a method called radiocarbon dating. The bombardment of the upper atmospher

e by cosmic rays converts nitrogen to a radioactive isotope of carbon, 14C, with a half-life of about 5730 years. Vegetation absorbs carbon dioxide through the atmosphere and animal life assimilates 14C through food chains. When a plant or animal dies, it stops replacing its carbon and the amount of 14C begins to decrease through radioactive decay. Therefore, the level of radioactivity must also decay exponentially. A parchment fragment was discovered that had about 68% as much 14C radioactivity as does plant material on Earth today. Estimate the age of the parchment. (Round your answer to the nearest hundred years.)
Chemistry
1 answer:
levacccp [35]3 years ago
3 0

Answer:

  • 28,700 years

1. Data:

a) Half-life: 5730 years

b) Final radioactivity: 68%

2. Solution:

a) <u>Determine the number of half-lives undergone</u>

  • Since, <em>the radioactivity has decreased to 68%, means that the carbon-14 contanined is has been reduced in </em> 32%: 100% - 68% = 32%.

  • 32 = 2⁵, meaning that five half-lives have passed since the <em>plant material</em> that formed the<em> parchment fragment died</em>.

b) <u>Compute the time of five half-lives</u>:

  • 5 × half-life time = 5 × 5730 years = 28,650 years.

c) <u>Round to the nearest hundred:</u>

  • 28,650 years ≈ 28,700 years

And that is <em>the age of the parchment</em>.

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**Check for proof photos at the bottom.**

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