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6 November, 21:49

A compound containing sodium, chlorine, and oxygen is 25.42% sodium by mass. A 3.25 g sample gives 4.33*1022 atoms of oxygen. What is the empirical formula?

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  1. 6 November, 22:58
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    step one

    calculate the % of oxygen

    from avogadro constant

    1moles = 6.02 x 10 ^23 atoms

    what about 4.33 x10^22 atoms

    = (4.33 x 10^ 22 x 1 mole) / 6.02 10^23 = 0.0719 moles

    mass = 0.0719 x16 = 1.1504 g

    % composition is therefore = (1.1504/3.25) x100 = 35.40%

    step two

    calculate the % composition of chrorine

    100 - (25.42 + 35.40) = 39.18%

    step 3

    calculate the moles of each element

    that is

    Na = 25.42 / 23=1.1052 moles

    Cl = 39.18 / 35.5=1.1037moles

    O = 35.40/16 = 2.2125 moles

    step 4

    find the mole ratio by dividing each mole by 1.1037 moles

    that is

    Na = 1.1052/1.1037=1.001

    Cl = 1.1037/1.1037 = 1

    0=2.2125 = 2

    therefore the empirical formula = NaClO2
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