a sample of potassium -40 has a mass of 12.5 grams. if the sample originally had 50 grams of potassium-40 at the start of radioactive decay, how many half lives have passed? the decay rate of potassium-40 is 1.3 billion years. how old is the sample?Can anyone help me figure half lives for my science homework?
Half-life is the time it takes for half the atoms to decay.
The original sample had 50 g of K-40
So after 1 half-life there would be 25 g of K-40 left
After 2 half-lives there would be 12.5 g of K-40 left
Because the original 50 g sample of K-40 now has 12.5 g of K-40, 2 half-lives have passed
If the half-life of K-40 is 1.3 billion years, then the sample is 2 x 1.3 billion years = 2.6 billion years old.
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