H3PO4 - Polyprotics Acid speciation as a function of pH...

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Polyprotics Acid speciation as a function of pH some terms defined  “TOTA” – the total amount of the acid A α i ” – the fraction of C HA  (TOTA) that has lost  i  protons { } { } 0 1 HA TOTA A TOTA - α = α = “0”: zero protons lost “1”: one proton lost { } { } TOTA HA A - = + (Adapted from a Univ. Colorado website)
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Polyprotics Solving for  α 0  and  α 1   For a given K a , speciation as a function of pH can  be plotted 0 1 { } { } { } a a a H K H K K H + + + α = + α = + { } log{ } log log { } log{ } log log { } a a a H HA TOTA K H K A TOTA K H + + - + = + + = + +
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-14 -12 -10 -8 -6 -4 -2 0 0 2 4 6 8 10 12 14 pH log C [H + ] [OH -] [H A or BH + ] [A- or B] Polyprotics log [ ]-pH diagrams TOTA (C HxA ) concentrations near TOTA except around pK a pK a at pH = pK a , {H + } = K a {HA} = {A - } = 0.5 TOTA 0 1 { } { } 0.5 { } { } { } 0.5 { } a a a a a a H H K H H H K K K H K K + + + + + + α = = = + + α = = = + +
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H3PO4 - Polyprotics Acid speciation as a function of pH...

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