250 mL of 0.245 M benzoic acid (HC7H5O2) is mixed with 350 mL of 0.195 M sodium benzoate (NaC7H5O2). What is the pH?

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  • 4 months ago

    pKa for benzoic acid = 4.19

    Let HBz = HC7H5O2 and Bz- = C7H5O2-

    [HBz]:

    M1V1 = M2V1

    0.245 (250) = M2 (600)

    M2 = [HBz] = 0.102 M

    [Bz-]:

    0.195 (350) = M2 (600)

    M2 = [Bz-] = 0.114 M

    pH = 4.19 + log (0.114 / 0.102) = 4.24

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