Question

cu exists as ⁶³cu and ⁶⁵cu calculate the abundance of each isotope when average mass of Cu 63.5 cu​

Answer 1

Answer:

Let, for 1 mole of Cu consisting of the two isotopes, the moles of Cu-63 be x moles. Then the amount of Cu-65 is (1-x) moles.

x times 63 + (1-x) times 65 = 63.5 to give the mixed-isotope mass

63x + 65 = 65x + 63.5

2x = 1.5

x = 0.75 mole

Cu-63 is 75% of the isotopic mix. The greater mole fraction of the lower mass isotope gives an average weighted towards the lower end.