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12 January, 19:39

The atomic masses of 204Pb (1.4 percent), 206Pb (24.1 percent), 207Pb (22.1 percent), and 208Pb (52.4 percent) are 203.973020, 205.974440, 206.975872, and 207.976627 amu, respectively. Calculate the average atomic mass of lead. The percentages in parentheses denote the relative abundances.

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Answers (2)
  1. 12 January, 19:55
    0
    207 amu

    Explanation:

    Given data

    Isotope Mass Relative abundance

    ²⁰⁴Pb 203.973020 amu 1.4% (0.014)

    ²⁰⁶Pb 205.974440 amu 24.1% (0.241)

    ²⁰⁷Pb 206.975872 amu 22.1% (0.221)

    ²⁰⁸Pb 207.976627 amu 52.4% (0.524)

    We can find the average atomic mass (AM) of an element using the following expression.

    AM = ∑mi * abi

    where

    mi is the mass of each isotope

    abi is the relative abundance of each isotope

    AM = 203.973020 amu * 0.014 + 205.974440 amu * 0.241 + 206.975872 amu * 0.221 + 207.976627 amu * 0.524

    AM = 207 amu
  2. 12 January, 22:32
    0
    207amu

    Explanation:

    To calculate the average atomic mass of an element you must multiply the masses of its isotopes with the percent abundance divided by 100. Then you add them together for your answer.

    203.973020amu * 0.014 = 2.9amu

    205.974440amu * 0.241 = 49.6amu

    206.975872amu * 0.221 = 45.7amu

    207.976627amu * 0.524 = 109amu

    2.9 + 49.6 + 45.7 + 109 = 207amu
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