After 2 half-lives, 25% of the original amount of thorium-234 will remain. This is because half of the substance decays in each half-life period.
After one half-life, half of the original amount of Uranium-235 would remain. After four half-lives, only ( \frac{1}{2^4} ) or ( \frac{1}{16} ) of the original amount would be left. Therefore, if you started with 100 grams of Uranium-235, 6.25 grams would remain after four half-lives.
Only 1/32 of the original radioactive material will remain. (½)5 = 1/32
The half-life of cesium-137 is approximately 30.1 years, not 2 years. After one half-life, 5 G of the original 10 G sample would remain. After two half-lives (about 60.2 years), 2.5 G would remain, and so on. If you meant a hypothetical isotope with a 2-year half-life, after 2 years, 5 G would remain, and after 4 years, 2.5 G would remain.
After each half-life, half of the radium-226 will decay. Therefore, after four half-lives, 1/2^4 or 1/16th of the original gram of radium-226 will remain unchanged. This means that 1/16th of a gram, or 0.0625 grams, will still be unchanged after four half-lives.
Potassium-40 has a half-life of approximately 1.25 billion years. After 3.9 billion years, which is about 3.12 half-lives (3.9 billion divided by 1.25 billion), the amount remaining can be calculated using the formula ( N = N_0 \times \left( \frac{1}{2} \right)^n ), where ( N_0 ) is the initial amount and ( n ) is the number of half-lives. Starting with 800 grams, after 3.12 half-lives, approximately 100 grams of potassium-40 would remain.
After one half-life, half of the original amount of Uranium-235 would remain. After four half-lives, only ( \frac{1}{2^4} ) or ( \frac{1}{16} ) of the original amount would be left. Therefore, if you started with 100 grams of Uranium-235, 6.25 grams would remain after four half-lives.
Only 1/32 of the original radioactive material will remain. (½)5 = 1/32
1g (1/2)4 = 1/16 g
After 4 half-lives, the amount remaining is ( (1/2)^4 ), which equals 1/16. Therefore, 1 gram of radium-226 will have 1/16 gram unchanged after four half-lives, which is 0.0625 grams.
The half-life of cesium-137 is approximately 30.1 years, not 2 years. After one half-life, 5 G of the original 10 G sample would remain. After two half-lives (about 60.2 years), 2.5 G would remain, and so on. If you meant a hypothetical isotope with a 2-year half-life, after 2 years, 5 G would remain, and after 4 years, 2.5 G would remain.
After three half-lives, 12.5% of the original radioactive material will remain. Each half-life reduces the amount of material by half, so after three half-lives the remaining material will be 0.5^3 = 0.125 or 12.5%.
After each half-life, half of the radium-226 will decay. Therefore, after four half-lives, 1/2^4 or 1/16th of the original gram of radium-226 will remain unchanged. This means that 1/16th of a gram, or 0.0625 grams, will still be unchanged after four half-lives.
To determine the remaining amount of a 200 gram sample after 36 seconds with a half-life of 12 seconds, we first calculate how many half-lives fit into 36 seconds. There are three half-lives in 36 seconds (36 ÷ 12 = 3). Each half-life reduces the sample by half: after the first half-life, 100 grams remain; after the second, 50 grams; and after the third, 25 grams. Therefore, 25 grams of the sample would remain after 36 seconds.
After two half-lives, 75% of the original material has decayed.
Potassium-40 has a half-life of approximately 1.25 billion years. After 3.9 billion years, which is about 3.12 half-lives (3.9 billion divided by 1.25 billion), the amount remaining can be calculated using the formula ( N = N_0 \times \left( \frac{1}{2} \right)^n ), where ( N_0 ) is the initial amount and ( n ) is the number of half-lives. Starting with 800 grams, after 3.12 half-lives, approximately 100 grams of potassium-40 would remain.
6 hours = 2 half lives, thus 25 % would remain. 0.25 x 2 mg = 0.5 mg.Done another way...fraction remaining = 0.5^n where n = number of half lives = 6hr/3hr = 2fraction remaining = 0.5^2 = 0.250.25 x 2 mg = 0.5 mg
After 2 half-lives (two half-lives of tritium is 12.32 x 2 = 24.64 years), the initial 10g sample of tritium would have decayed by half to 5g.