2.66666666666667 grams
39
59.25 secondsAfter 1 half-life: 16*(1/2) = 8 g remainsAfter 2 half-lives: 8*(1/2) = 4g remainsAfter 3 half-lvies: 4*(1/2) = 2g remainsAfter 4 half-lives: 2*(1/2) = 1g remainsSo after 4 half-lves you have 1 gram of Na25 left. This is also the amount remaining after 237 seconds. Since 4 half-lives have elapsed over 237 seconds, you can divide 237 seconds by 4 to find the half-life of Na25 is 59.25 seconds.You can also figure it out using the rate of decay formula:At = Ao*e-ktwhere Ao is the initial amount, At is the amount left after some time t. k is the decay constant which is k = ln 2 / t1/2 where t1/2 is the half-life.In this case Ao = 16g, At = 1g, t=237 secSubstitute in the formula to solve for k, then take the answer for k and use it in the other formula to solve for the half-life (t1/2):1 = 16*e-237kln (1/16) = ln (e-237k)-2.7726 = -237kk = -2.7726/-237 = 0.011699 sec-1t1/2 = ln 2/k = 0.693147/0.011699 sec-1t1/2 = 59.25 sec
1/8 amount of the element will reamain. After 1 half-life there is 1/2 left After the 2nd half-life there is 1/2 of 1/2 left which is 1/4 After the 3rd half-life there is 1/2 of 1/4 left which is 1/8
It is a half left side triangle, nothing more, nothing less.
This question cannot be answered. This does not make any sense.
After the first half-life, you will have one half of the starting amount. After a second half-life period, you'll be down to one quarter. Of the part that radioactively decays, about 11% of it will decay to 40Ar, and the remainder to 40Ca. Of your total sample of ordinary potassium, only 0.012% will be 40K. The half-life of 40K is about 1.3x109 years.
1/16 of the original sample of any unstable element remains after 4 half lives.
If I take a radioactive sample of 400 moles of an unknown substance and let it decay to the point of three half-lives I would have 50 moles left of the sample. 1/2 of what is left will decay in the next half-life. At the end of that half-life I will have 25 moles left of the unknown substance or 4/25.
Half-life is the length of time required for half the atoms in a radioactive sample to decay to some other type of atom. It is a logarithmic process, i.e. in one half-life, there is half the sample left, in two half-lives there is one quarter the sample left, in three half-lives there is one eight left, etc. The equation is... AT = A0 2 (-T/H) ... where A is activity, T is time, and H is half-life.
The half-life is 2 days. You start with 100 grams. In one half life, you will lose 50 grams and have 50 grams remaining. In a second half-life, you will lose 25 of the 50 grams and have 25 grams left. You will have lost 75 grams of a 100 gram sample of radioactive material and have only 25 grams of it left after two half-lives. That means there are two half-lives from 9 a.m. Monday to 9 a.m. Friday. That's 4 days for 2 half-lives, or 2 days for one half-life.
12.5 g
Hi, Each half-life means the mass of the sample has decreased by 1/2 its mass. Thus; After 1 half-life, 1/2 the sample has decayed. After 2 half-lives 3/4 of the sample has decayed. Hope this helps.
3 At the end of the first half life, there will theoretically be 50% remaining. 2 half lives: 25% 3 half lives:12.5 %
If a sample of radioactive material has a half-life of one week the original sample will have 50 percent of the original left at the end of the second week. The third week would be 25 percent of the sample. The fourth week would be 12.5 percent of the original sample.
Eight days would be four half-lives. One-half to the fourth power is one-sixteenth. So you would have half a gram left.
1/8th gram will be left. That's your answer.
You start with 5 grams- every 8 days, half of what is there goes away. At 8 days. there will be 2.5 grams. At 16 days, half of THAT is gone- now down to 1.25 grams. At 24 days, half of THAT is gone, leaving 0.625 grams. At 32 days, you have half of 0.625 grams. so divide .625 by two and you get .3125.