Chapter 10: Q35P (page 232)

Fractional composition in a triprotic system. For a triprotic system, the fractional composition equations where are $D = {[H^{+}]}^{3} + K_{1} {[H^{+}]}^{2} + K_{1} K_{2} [H^{+}] + K_{1} K_{2} K_{3}$ Use these equations to create a fractional composition diagram analogous to Figure 10-4 for the amino acid tyrosine. What is the fraction of each species at $pH 10.00$ ?
$α_{H_{3} A} = \frac{{[H^{+}]}^{3}}{D} α_{H^{2}} = \frac{K_{1} K_{2} [H^{+}]}{D} α_{H_{2} A} = \frac{K_{1} {[H^{+}]}^{2}}{D} α_{A^{3}} = \frac{K_{1} K_{2} K_{3}}{D}$

Short Answer

Expert verified

The values in cells D2, E2, F2 and G2 are calculated via:

$D 2 = C 2^{3} / (C 2^{3} + C 2 * A 2 + C 2 * A 2 * A 4 * A 2 * A 4 * A 6) E 2 = C 2^{2} * A 2 / (C 2^{3} + C 2 * A 2 + C 2 * A 2 * A 4 * A 2 * A 4 * A 6) F 2 = C 2 * A 2 * A 4 / (C^{3} + C 2 * A 2 + C 2 * A 2 * A 4 + A 2 * A 4 * A 6) G 2 = A 2 * A 4 * A 6 / (C 2^{3} + C 2 * A 2 + C 2 * A 2 * A 4 + A 2 * A 4 * A 6)$

Step by step solution

Fractional Composition of diprotic system

The dominant and minor species in solution are clearly visible in fractional composition.
Fractional compositions allow you to see what reactions are taking place and which ones aren't as essential.
Fractional compositions make for some extremely interesting plots.

Create a spreadsheet.

Fractional composition in a triprotic system. The given equations in order to create a fractional composition diagram for the amino acid tyrosine. Also, we will determine the fraction of each species at pH = 10.00 .

The final spreadsheet is shown below: