Question
If a rock sample was found to contain $1.16 \times 10^{-7} \mathrm{~mol}$ of argon- 40 , how much potassium- 40 would also have to be present for the rock to be $1.3 \times 10^{9}$ years old?
Step 1
3 \times 10^{9}$ years. This means that after this period of time, half of the potassium-40 will have decayed into argon-40. Show more…
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If a rock sample was found to contain $1.16 \times 10^{-7} \mathrm{~mol}$ of argon-40, how much potassium- $40\left(t_{1 / 2}=1.3 \times 10^{9} \mathrm{yr}\right)$ would also have to be present for the rock to be $1.3 \times 10^{9}$ years old? See assumption in Problem 13.91 .
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