Naturally occurring copper consists of copper-63 (62.9296 amu), and copper-65 (64.9278 amu). Using the relative atomic mass from the periodic table, which of the following is the best estimate of the percent abundance of the two isotopes of copper?

Question

Quizplus · Accepted Answer

The average atomic mass of copper on the periodic table is 63.55 amu, which is closer to the mass of copper-63. This suggests that there must be a higher abundance of copper-63. Based on the masses given for copper-63 and copper-65, we can calculate the weighted average as follows:
(0.75)(62.9296 amu) + (0.25)(64.9278 amu) = 63.55 amu
Therefore, the best estimate of the percent abundance is 75% copper-63 and 25% copper-65.

Naturally Occurring Copper Consists of Copper-63 (62