Chemistry

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The rate of a first-order reaction is followed by spectroscopy, monitoring the absorption of a colored reactant at 520 nm . The reaction occurs in a 1.29-cm sample cell, and the only colored species in the reaction has an extinction coefficient of 5700 cm-1M-1 at 520 nm .

a) Calculate the initial concentration of the colored reactant if the absorbance is 0.564 at the beginning of the reaction.

b) The absorbance falls to 0.254 at 30.0 min . Calculate the rate constant in units of s-1.

c) Calculate the half-life of the reaction. (in sec)

d) How long does it take for the absorbance to fall to 0.104? (in sec)

  • Chemistry -

    a) A = ebc
    A = 0.564
    e = 5700
    b = 1.29
    c = ?

    b) A = ebc
    A = 0.254
    e = 5700
    b = 1.29
    c = ? at 30 min.
    Convert delta C to delta C/second and rate = k*c

    c)
    k = 0.693/t1/2
    You have k, solve for t1/2.

    d) A = ebc
    A = 0.104
    e = 5700
    b = 1.29
    c = ?

    Then ln(No/N) = kt
    No = from part a.
    N = from part d.
    k = from part b.
    t = ? in seconds if b is in sec.

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