A certain radioactive substance has a half-life of 10 years. If the original sample weighted 20 grams and 20 years have passed, how many grams of the sample should be left?
B.
Tying into the question above in another 10 years, how many grams of the sample should be left?
2006-12-13 02:42:34 · 2 answers · asked by cetinnovations 1 in Science & Mathematics ➔ Chemistry
ok..
20grms-----------------10gms------------------5gms in 20 yrs..
in 30 yrs, it becomes 2.5 grams...
just calculate the no. of half lives..
2006-12-13 02:46:06 · answer #1 · answered by For peace 3 · 0⤊ 0⤋
A raidoactive substance will disintegrate into half of its initial weight in a time known as half-life. Therefore the substance having a half-life of 10 years which weighed 20 grams 20 years ago would have decayed into 10 grams in 10 years and those 10 grams would have decayed into 5 grams in the next 10 years. So the substance would now weigh 5 grams. By the same calculation in another 10 years half of these 5 grams would have decayed into 2.5 grams. So only 2.5 grams of the substance would be left.
Theoretically a radioactive substance would last upto infinity.
2006-12-13 03:02:40 · answer #2 · answered by naina 2 · 1⤊ 0⤋