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Chemistry

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1) Frank and Oswalt report a molar absorptivity of 4700 L mol^-1 cm^-1 for thiocyanatoiron(lll) ion. What absorbance would you expect for a soloution that it 1.0e-4 M in thiocyanatorion(lll) ion, if the path length is 1.00 cm?

2) At a given temperature, the equilibrium constant for the system studied in this experiment is 1.40e+2. Suppose 100.0 ml of 2.00e-3 M KSCN was mixed with 100.0 ml of 2.00e-3 M Fe(NO_3_)_3_. At equilibrium, what molar concentration of the thiocyanatoiron(lll) ion would you expect?

  • Chemistry -

    A = abc
    A = 4700*1*1E-4
    Solve for absorbance.

    100 mL x 2E-3 = 0.2 millioles Fe^3+
    100 mL x 2E-3 = 0.2 millimols SCN^-
    (Fe^3+) = 0.2 mmols/200 mL = 0.001M
    (SCN^-) = likewise = 0.001M
    .......SCN^- + Fe^3+ ==> FeSCN^2+
    .....0.001....0.001.......0
    C......-x.......-x.........x
    E....0.001-x..0.001-x......x

    Keq = 140 = (FeSCN^2+)/(SCN^-)(Fe^3+)
    Substitute from the E line and solve for x

  • Chemistry -

    2.00x10^-3

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