Isotope questions

[Smooth Operater]

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hello,

69% of naturally occuring copper is copper-63. If only one other isotope is present in natural copper, what is it?

a. copper-61
b. copper-62
c. copper-64
d. copper-65

answer is D, but how would you solve it?

does isotope questions actuallly show up one real exam?

 

[student253]

I've seen similar questions like this in Destroyer, I don't think there will be much variation to this problem.

Atomic Weight= (%)(Isotope 1) + (%)(Mass Isotope 2) + (%)(MassIsotope n)

63.546= (.69)(63) +(.31)(Isoptope 2)

It comes out to be 64.76 ~ 65.

Hope that helps!