chemistry

A 1.11 M solution of fluoroacetic acid, FCH2CO2H, is 5% dissociated in water. Calculate the value of the pKa of FCH2CO2H.

pKa:

?? I dn't even know how to strt with this

asked by WIll
  1. Let's call fluoroacetic acid HFAc. Then
    .........HFAc ==> H^+ + FAc^-
    I.......1.11......0......0
    C.....-0.055....0.055...0.055
    E......you do it..0.055..0.055

    Ka = (H^+)(FAc^-)/(HFAc)
    Substitute the E line into Ka expression and solve for Ka, then convert to pKa.
    Note: The acid is 5% dissociated, therefore, every 100 mols dissociates to give 5 of each ion and leaves 95 undissociated molecules. Therefore, M x 0.05% gives you the ion M and 1.11- that gives you the undissociated part.

    posted by DrBob222
  2. got it!
    ka= 3.26*10^-3
    so pKa=2.49

    tnx

    posted by Will

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