Question

A Copper cube weighs 146.314 grams. You have Isotope Cu-63 (60.91% abundance) and Isotope Cu-65 (30.19% abundance). What is the mass of both Isotopes, Cu-63 and Cu-65?

Answer 1

total mass = (percent abundance of Cu-63)(mass of Cu-63) + (percent abundance of Cu-65)(mass of Cu-65)

this equation has two unknowns (the masses of both isotopes) so you would use the total mass to convert everything into one unknown

for example, mass of cu-65 = total mass - unknown of cu-63

doing this replacement will convert everything to one variable

Answer 2

I wrote down the following: (0.6091)(x) + (0.3019)(0.9038-x) = 146.314

Answer 3

oh, the percentages don't add up to 100, this changes things a bit

let me think...

Answer 4

and I got x=475.3943451, therefore something is wrong because it should give me a smaller value like 63.

Answer 5

and I was thinking about converting it to amu, but I do not know how to convert grams to amu.

Answer 6

here's what I was thinking originally:

146.314 = (60.91/100)x + (30.19/100)(146.314-x)

Answer 7

however, the fact that they don't add up to 100% changes the situation a bit :S

Answer 8

let me solve for x.

Answer 9

it cannot be that equation because it gives me a value of about 300 and something.

Answer 10

@sweetburger can you take a look at this when you have a chance, my gen chem has gone down the drain