Isotope abundance

1. Strontium has four stable isotopes Strontium-84 has a very low natural abundance, but Sr-86, Sr-87, and Sr-88 are all reasonably abundant. Knowing that the atomic weight of strontium is 87.62, which of the more abundant isotopes predominates?

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Strontium has an atomic weight of 87.62 so 88Sr is the most abundant.

 

2. Silver (Ag) has two stable isotopes, 107Ag and l09Ag
The isotopic weight of l07Ag is l06.9051, and the isotopic mass of l09Ag is 108.9047 The atomic weight of Ag, from the pen`odic table, is 107.868, Estimate the percent of 107Ag in a sample of the element
a) 0% b) 25% (c) 50 (d) 75%

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(c) 50% Actual value is 51.84%

 

3. Copper exists as two isotopes: 63Cu (62.9298 u) and 65Cu (64.9278 u)
What is the approximate percent of 63Cu in samples of this element?
(a) I0% (c) 50% (e) 90%
(b) 30% (d) 70%

Show Answer
(d) 70% Actual value is 69.17%

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