6.25
Since half of the atoms of the original substance will have decayed after 5 hours, half of what is left will have decayed after the next five hours. The answer is 0.25 or one fourth of the original atoms will remain.
6 hours. you have a hot one there!
Twice the half-life.
The half-life of a radioactive substance is the time that it takes for half of the atoms to decay. With a half-life of 10 days, half has decayed in this time. After 20 days, a further 10 days/another half life, a further half of the remainder has decayed, so 1/4 of the original material remains, 1/4 of 15g is 3.75 grams. This is the amount of original radioactive substance remaining, but it’s daughter isotope ( what the decay has produced ) is also present, so the original sample mass is effectively constant, especially in a sealed container. Even in an unsealed container, and assuming alpha ( helium nucleii) emission, a drop in mass per radioactive atom of 4 Atomic Mass units, compared with the original atom of, say 200 amu is only 2% mass decrease, less for heavier decaying nucleii.
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.
The half-life of a radioactive substance that decays from 2.4g to 1.8g in 66 hours is 159 hours. AT = A0 2(-T/H) 1.8 = (2.4) 2(-66/H) 0.75 = 2(-66/H) log2(0.75) = log2(2(-66/H)) -0.415 = -66/H H = 159
Its 5 hours. 50% of the substance is decayed at 10 hours (that is what half life means. It's full life is 20 hours). Multiple 75% times 20 hours to find that 75% is 15 hours. Subtracrt 15 hours from 20 hours to get the answer of 5 hours for the decay of 75% of the substance.
U-238 --> alpha + gamma + Th-234, halflife 4.51E9 yearsTh-234 --> beta- + gamma + Pa-234, halflife 24.10 daysPa-234 --> beta- + gamma + U-234, halflife 6.66 hours
The duration of Radioactive Dreams is 1.63 hours.
Hvbh
Using the formula Nt = N0*(1/2)t/t1/2 where Nt is the amount of stuff remaining after an amount of time, t, and t1/2 is the half-life, you get Nt = .036N0. So about 3.6% of the radioactive stuff is left.
125