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Calculating Half Life of Radioactive Isotopes: Solved Examples, Lecture notes of Chemistry

Fashion Institute of Design & Merchandising (FIDM) - Orange CountyChemistry

Step-by-step solutions to calculate the half-life of radioactive isotopes using examples. Students will learn how to determine the number of half-lives based on the given data and find the original sample size.

Typology: Lecture notes

2021/2022

Uploaded on 09/12/2022

danmarino
danmarino 🇺🇸

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Calculating Half Life
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Download Calculating Half Life of Radioactive Isotopes: Solved Examples and more Lecture notes Chemistry in PDF only on Docsity!

Calculating Half Life

Half Life Practice

  1. If 20.0 g of a radioactive isotope are present at 1:00 PM and 5.0 g remain at 2:00 PM, what is the half life of the isotope?
  2. If we start with 400 atoms of a radioactive substance, how many would remain after one half-life? 2 half- lives, 3 half- lives, 4 half lives?
  3. A sample of carbon-14 has been decaying for 22,920 years and is now 35.0 grams. What was the size of the original sample? (The half-life of carbon-14 is 5,730 years)
  1. If we start with 400 atoms of a radioactive substance, how many would remain after one half-life? 2 half- lives, 3 half- lives, 4 half lives?
  • After 1 half- life 200
  • After 2 half-lives? 100
  • After 3 half-lives? 50
  • After 4 half-lives? 25

A sample of carbon-14 has been decaying for 22,920 years and

is now 35.0 grams. What was the size of the original sample?

(The half-life of carbon-14 is 5,730 years)

  • 22920/5730 = 4 half lives
  • You will need to work backwards 35  70  140  280  560. grams