Naturally occurring element X exists in three isotopic forms: X-28 (27.977 amu, 92.23% abundance), X-29 (28.976 amu, 4.67% abundance), and X

Question

Naturally occurring element X exists in three isotopic forms: X-28 (27.977 amu, 92.23% abundance), X-29 (28.976 amu, 4.67% abundance), and X-30 (29.974 amu, 3.10% abundance). Calculate the atomic weight of X. A. 86.93 amu B. 48.63 amu C. 28.09 amu D. 28.97 amu E. 27.16 amu

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Nguyệt Ánh 4 years 2021-08-29T03:02:31+00:00 1 Answers 44 views 0

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  1. mit
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    2021-08-29T03:03:58+00:00
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    Answer:

    C. 28.09 amu

    Explanation:

    The natural occurring element exist in 3 isotopic forms: namely X-28 (27.977 amu, 92.23% abundance),  X-29 (28.976 amu, 4.67% abundance) and  X-30 (29.974 amu, 3.10% abundance).

    The atomic weight of elements depends on the isotopic abundance. If you know the fractional abundance and the mass of the isotopes the atomic weight can be computed.

    The atomic weight is computed as follows:

    atomic weight = mass of X-28 × fractional abundance + mass of X-29 × fractional abundance + mass of  X-30 × fractional abundance

    atomic weight = 27.977 × 0.9223 + 28.976 × 0.0467 + 29.974 ×  0.0310

    atomic weight = 25.8031871 + 1.3531792 + 0.929194

    atomic weight = 28.0855603 amu

    To 2 decimal place atomic weight = 28.09 amu

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