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WorksheetsHalf Life Calculations
Total questions: 25
Worksheet time: 25mins
What is the half-life of iodine-131?
32 days
8 days
16 days
24 days
The % of the parent isotope remaining after 1 Half Life.
50%
25%
12.5%
6.25%
The diagram shows 32 atoms
32 of the Red are the parent isotope
0 of the atoms are daughter isotopes
How many half-lives have occurred?
0
1
2
3
The diagram shows 32 atoms.
16 of the Red are parent isotopes
16 of the Green are daughter isotopes
How many half-lives have occurred?
0
1
2
3
If 20 g of copper-64 has a half-life of 13 hours, what mass of copper-64 will remain after 26 hours?
20 g
10 g
5 g
2.5 g
How many seconds does it take a 100.0g sample of Arsenic-81, with a half-life of 33.0 seconds, to decay to 6.250g?
How much of an 80 g sample will remain after 21.2 years?
40 g
20 g
10 g
5 g
An isotope of cesium 138 has a half-life of 30 years. If 1.00 g of cesium-138 disintegrates over a period of 90 years, how many grams of cesium-138 would remain?
A radioactive isotope has a half-life of 2.5 years. Match the correct fraction of the original mass that remains unchanged after the given amount of years
12.5 years
1/32 radioactive
10 years
1/16 radioactive
7.5 years
1/8 radioactive
5 years
1/4 radioactive
2.5 years
1/2 radioactive
When an isotope goes through 2 half-lives, _____ _________________ remains
1/4 or 25%
1/2 or 50%
1/8 or 12.5%
What percent of carbon-14 would be left after 11,460 years?
100%
75%
50%
25%
When an isotope goes through 4 half-lives, _____ _________________ remains
1/4 or 25%
1/8 or 12.5%
1/16 or 6.25%
You have 100 grams of radioactive C-14. The half life of C-14 is 5715 years.
How many grams are left after each half life?
1 half life
50g or 1/2
2 half lives
25g or 1/4
3 half lives
12.5g or 1/8
4 half lives
6.25g or 1/16
You collected a sample of a rock and it had 25% remaining of a radioactive element with a half life of 60 years. How old was that rock sample?
(a)
If 20 g of copper-64 has a half-life of 13 hours, what mass of copper-64 will remain after 39 hours? ( Drag the answer to the space.) (a)
2.5 g
20 g
10 g
1.25 g
5 g
0.625
Ge-81 emits beta particles and has a half-life of 7.6 seconds.
Determine the time required for a 16.00-gram sample of Ge-81 to decay until only 1.00 gram of the sample remains unchanged.
1 grams
1/16 radioactive
2 grams
1/8 radioactive
4 grams
1/4 radioactive
8 grams
1/2 radioactive
16 grams
Completely radioactive
What is the Half life of this isotope?
5 seconds
10 seconds
15 seconds
20 seconds
What is the Half Life of this isotope?
3 days
5 days
8 days
10 days
Imagine you have 50,000 atoms of uranium-238. If U-238 has a half-life of 4.5 billion years, how many U-238 atoms will be left after 4.5 billion years?
25,000
50,000
12,500
0
The mass of a parent isotope is 100 g. How many grams of the parent isotope will remain after 2 half-lives?
25
50
12.5
0
A 50.0 g sample of a radioactive element has a half-life of 40 years. How much mass will be left after 80 years?
50
25
12.5
6.25
A radioactive substance has a half-life of 10 years. If you start with 80 grams, how much will remain after 30 years?
10 grams
20 grams
40 grams
5 grams
The half-life of a certain isotope is 5 years. If you have 200 grams initially, how many grams will remain after 15 years?
25 grams
50 grams
100 grams
12.5 grams
A scientist measures a sample and finds that only 1/8 of the original radioactive material remains. If the half-life of the material is 3 years, how many years have passed?
3 years
6 years
9 years
12 years
If a radioactive isotope has a half-life of 8 days, how many days will it take for a sample to decay from 160 grams to 10 grams?
24 days
32 days
40 days
48 days
