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An element, X has the following isotopic composition: 200X: 90%; 199X: 8.0%; 202X: 2.0%. The weighted average atomic mass of the naturally occurring element X is closest to:

1. 201 amu
2. 202 amu
3. 199 amu
4. 200 amu

Correct answer: 200 amu

Solution

The weighted average atomic mass is calculated as (200 × 0.90) + (199 × 0.08) + (202 × 0.02) = 200 amu. Thus, the closest value is 200 amu.

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