copper

[methlover]

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

choices:
A)copper-61
B)copper-62
C)copper-64
D)copper-65

Here is how I tried to solve this problem. I looked at the periodic table, and the atomic weight for copper is 63.5g/mol. So I can eliminate choice A and B. Now I am left with copper-64 and copper-65. Since copper 64 is close to 63.5g/mol than copper 65, isn't copper-64 the other isotope present in natural copper??

I don't even remember learning this in gen. chem. Someone try to explain why it's copper-65 instead of copper-64 because the book's explanation didn't help me much.

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[sleepy425]

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

choices:
A)copper-61
B)copper-62
C)copper-64
D)copper-65

Here is how I tried to solve this problem. I looked at the periodic table, and the atomic weight for copper is 63.5g/mol. So I can eliminate choice A and B. Now I am left with copper-64 and copper-65. Since copper 64 is close to 63.5g/mol than copper 65, isn't copper-64 the other isotope present in natural copper??

I don't even remember learning this in gen. chem. Someone try to explain why it's copper-65 instead of copper-64 because the book's explanation didn't help me much.

so the atomic weight is the average weight of all the isotopes of an atom. so if 69% is copper-63, if the only other isotope is copper 64, the average shouldn't be exactly in between 63 and 64, right? it should be closer to 63, because it's just like saying, I have 10 numbers, 7 of which are 63, and 3 of which are 64. The average won't be 63.5, it'll be closer to 63. So it has to be the heavier isotope, which will raise the average to 63.5.

 

[dwc929]

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

choices:
A)copper-61
B)copper-62
C)copper-64
D)copper-65

Here is how I tried to solve this problem. I looked at the periodic table, and the atomic weight for copper is 63.5g/mol. So I can eliminate choice A and B. Now I am left with copper-64 and copper-65. Since copper 64 is close to 63.5g/mol than copper 65, isn't copper-64 the other isotope present in natural copper??

I don't even remember learning this in gen. chem. Someone try to explain why it's copper-65 instead of copper-64 because the book's explanation didn't help me much.

Mathematically: (0.69)(63) = 43.47...(0.31)(x) = 63.5-43.47
x = 65