Question

A volcanic eruption melts a large area of rock, and all gases are expelled. After cooling, ⁴⁰Ar (atomic number 18) accumulates from the ongoing decay of ⁴⁰K (atomic number 19) in the rock (t_1/2 = 1.25 × 10⁹ yr). When a piece of rock is analyzed, it is found to contain 1.08 mmol of ⁴⁰K and 1.38 mmol of ⁴⁰Ar. How long ago did the rock cool? Enter your answer in scientific notation.

Answer 1

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