Geologist know that potassium 40 decays to argon 40, with a half life of 1.3 billion years. analysis of a hypothetical sample of granite reveals that 75 percent of the potassium 40 atoms have decyaed to form argon 40. what is the age of the sample of granite
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Ответ:
First let us calculate for the rate constant k from the formula:
k = ln(2) / t0.5
where t0.5 is the half life
k = ln(2) / 1.3x10^9 years
k = 5.33x10^-10 years-1
Then we use the formula:
A/Ao = e^-kt
where A/Ao is the amount remaining = 25% = 0.25, t is time
Rearranging to get t:
t = ln(A/Ao) / -k
t = ln(0.25) / (-5.33x10^-10 years-1)
t = 2.6x10^9 years
Ответ:
29
Explanation:
since protons are a constant and unique characteristic of an element it's considered as he atomic number of that element.