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How many half-lives does it take for a radioactive substance to decay to 12.5 percent of its original amount?
Wiki User
∙ 15y ago
Without posting the actual formula and working it through, let's "step through" this and figure it out. Here are the steps to finding the length of time for the amount of radionuclide to decay to about 5% its original quantity: For the 1st half-life, 50% is left. Then 25%, then 12.5%, then 6.25%, then 3.125%. That's 5 half-lives, and after a bit over 4 half-lives, you'll be down to the 5% figure. The 4 half-lives is 4 x 12 or 48 hours. So in a bit over 2 days, you're down to 5% of the original amount of this substance left. There might (and probably will) be some removal of the material through normal body processes over this time. The translation is that the rate at which the substance leaves your body is going to vary. Going through the actual formula doesn't make sense from the point of view of the Biology. You ability to "get rid" of the substance will depend on what it is that you're been given and how quickly you can excrete it physiologically. That's in addition to radioactive decay. This substance, whatever it is, leaves you in those two ways. One is radioactive decay, and you will get a bit of radiation from that. The other is that your body dumps it before it decays. The ball park figure of two days stands as probably a "best answer" here. That's because even an "exact" calculation through mathematics ignores the physiological processes that will also help remove this material.
Wiki User
∙ 14y ago
Wiki User
∙ 15y ago3
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When the amount of a radioactive substance is reduced by 50 percent what has occurred?
Half-Life APEX (; xoxo
How old is a fossil that has a radioactive material with a half life of 200 years if there is 25 percent of the original radioactive material left?
400 yrs
If 10 percent of a radioactive substance disintegrates in 4 days what is it's half-life?
20 days
Tritium has a half life of 12.3 years if 118mg escapes what percent of the spill will remian radioactive in 61.5 years?
3.13% will be radioactive at that point.
How is tossing a coin similar to radioactive decay of an element?
If you toss a coin, there are fifty percent chances of getting the head or tail. In the radioactive decay also fifty percent atoms will brake down. When you toss the coin next time, you have 25 percent chances of getting the head or tail repeated. Same is the case with radioactive material. you will be left with 25 percent of the radioactive material after half life. Third time the chances of getting the same head or tail is 12.5 percent. Here you are left with 12.5 percent of the radioactive material left with after another half life.
When the amount of a radioactive substance is reduced by 50 percent what has occurred?
Half-Life APEX (; xoxo
How old is a fossil that has a radioactive material with a half life of 200 years if there is 25 percent of the original radioactive material left?
400 yrs
If 10 percent of a radioactive substance disintegrates in 4 days what is it's half-life?
20 days
A sample of a radioactive substance decayed to 95 percent of its original amount after a year.what is the half life of the substance?
The half-life of a radioactive nuclide when 95% of it is left after one year is 13.5 years. AT = A0 2(-T/H) 0.95 = (1) 2(-1/H) ln2(0.95) = -1/H H = -1/ln2(0.95) H = 13.5
What is a half-life of radioactive substance if it takes 6 hours for 50 percent of it to decay?
6 hours. you have a hot one there!
How many half-lives have passed for 50 percent of the original radioactive material?
One half-life.
If the half-life of a radioactive substance is 10 hours how long will it take for 50 percent of it to decay?
The half-life of a radioactive isotope is defined as the time taken for the isotope to decay to half of its initial mass. So to decay to 50 percent of its initial mass will take one half-life of the isotope. One half-life of the isotope is 10 hours so the time taken to decay is also 10 hours.
How many half-lives will it take for all but 25 percent of the original C-14 to decay?
39
What does a percent composition tell you about a substance?
It tells you what the substance is made of.
What is mole percent?
Mole percent, or molar percent of a substance is the ratio of the moles of a substance in a mixture to the moles of the mixture. It represents the number of moles of a substance in a mixture as a percentage of the the total number of moles in the mixture. Mole % = (mol substance in a mixture) / (mol mixture) * 100
Tritium has a half life of 12.3 years if 118mg escapes what percent of the spill will remian radioactive in 61.5 years?
3.13% will be radioactive at that point.
After three half-lives what percent of the radioactive isotope is remaining?
12.5% is remaining.
