Rhenium has two naturally occurring isotopes, ¹⁸⁵Re and ¹⁸⁷Re. The relative atomic mass of rhenium is 186.2. What are the natural abundances of these isotopes?
40 % ¹⁸⁵Re and 60 % ¹⁸⁷Re
60 % ¹⁸⁵Re and 40 % ¹⁸⁷Re
12 % ¹⁸⁵Re and 88 % ¹⁸⁷Re
88 % ¹⁸⁵Re and 12 % ¹⁸⁷Re
📝 Detailed explanation
Let x be the fraction of ¹⁸⁵Re. Then 185x + 187(1 − x) = 186.2. Solving gives x = 0.4, so the abundances are 40% ¹⁸⁵Re and 60% ¹⁸⁷Re.
