Answer to Question #138282 in General Chemistry for Mark Beshara

Question

The average atomic weight of copper is 63.5 amu. Copper has two naturally occurring isotopes. One of theisotopes has an atomic weight of 62.9 and an abundance of 69.1%. The other isotope has an abundance of30.9%. What is the atomic weight of this isotope?

Answer 1

decision
Ar (average) = Ar(1)* W +Ar (2) * W
Ar (1) = 62,9  W = 69,1% = 0,691
Ar(2)= Х   W=30,9% = 0,309

63,5=62,9 * 0,691 + Х * 0,309

63,5= 43,4639 + 0,309Х

0,309Х = 20,0361

Х = 64,84

answer: 64,84