Copper exists in two naturally occurring isotopes. The average atomic weight of copper is 63.546 amu. If 69.15% exists as 63cu with an atomic mass of 62.92, then what is the atomic mass of the second isotope?

Question

Chemistry

Alvin Sparks

6 January, 05:11

Copper exists in two naturally occurring isotopes. The average atomic weight of copper is 63.546 amu. If 69.15% exists as 63cu with an atomic mass of 62.92, then what is the atomic mass of the second isotope?

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Answers (2)

Know the Answer?

Luke Summers · Answer 1

Answer: Ar (Cu-second isotope) = 64.95

Explanation:

that is the correct answer

Justine Mckee · Answer 2

Answer is: the atomic mass of the second isotope is 64.95 amu (Cu-65).

Ar (Cu) = 63.546 amu; the average atomic weight of copper.

Ar (Cu-63) = 62.92; he average atomic weight of copper-63.

ω (Cu-63) = 69.15% : 100% = 0.6915.

ω (Cu-second isotope) = 100% - 69.15%.

ω (Cu-second isotope) = 30.85 % : 100% = 0.3085.

Ar (Cu) = Ar (Cu-63) · ω (Cu-63) + Ar (Cu-second isotope) · ω (Cu-second isotope).

63.546 amu = 62.92 amu · 0.6915 + Ar (Cu-second isotope) · 0.3085.

Ar (Cu-second isotope) · 0.3085 = 63.546 amu - (62.92 amu · 0.6915).

Ar (Cu-second isotope) · 0.3085 = 20.037.

Ar (Cu-second isotope) = 20.037 : 0.3085.

Ar (Cu-second isotope) = 64.95.