As uranium-238 decays it becomes lead 206. After 3.5 g of uranium decays for 1.125 time 10 to the 9th power, how many grams of the sample will be lead-206
EXTRA INFO- the half life for Uranium 238 is 4.5 billoin years
2007-01-03 11:41:41 · 2 answers · asked by Anonymous in Science & Mathematics ➔ Mathematics
1,125,000,000/4,500,000,000 x 3.5grams...seems fairly straight forward??
2007-01-03 11:48:54 · answer #1 · answered by Anonymous · 1⤊ 1⤋
1. Figure out how many years in 1.125 x 10^9, and divide by 4.5 billion to get the number of half lives that have passed.
2. Take 0.5 to the power of the number found in step 1. That is the fraction of the original U238 that remains.
3. Take the fraction found in step 2, and multiply by 3.5 g to find the mass of the U238 that remains.
Two notes:
- Easygoing is using the wrong formula. If you apply his method, you will get MORE uranium as time passes, rather than less.
- You didn't say what the units are for 1.125 x 10^9, but they're probably years, which means that the period in question is one fourth of one half life. So you'll want to take 0.5 to the .25 power (which will give you a number not much less than one (and a mass not much less than 3.5 g).
2007-01-03 11:49:38 · answer #2 · answered by actuator 5 · 2⤊ 1⤋