Question 10.3: Write a balanced equation for the proton-transfer reaction b...

Write a balanced equation for the proton-transfer reaction between phosphate ion (PO_4  ^{3-}) and water, and determine in which direction the equilibrium is favored.
ANALYSIS Look in Table 10.1 to see the relative acid and base strengths of the species involved in the reaction. The acid base proton-transfer equilibrium will favor reaction of the stronger acid and formation of the weaker acid.

ACID		CONJUGATE BASE
	\pmb{Strong  acids:  100\%  dissociated} \begin{cases} Perchloric  acid  & HClO_4 \\ Sulfuric  acid & H_2SO_4 \\ \\ Hydriodic  acid & HI \\ Hydrobromic  acid & HBr \\ Hydrochloric  acid & HCl \\ Nitric  acid & HNO_3 \end{cases}	\left. \begin{matrix} ClO_4  ^- & Perchlorate  ion \\ HSO_4  ^- & Hydrogen \\ &     sulfate  ion \\ I^- & Iodide  ion \\ Br^- & Bromide  ion \\ Cl^- & Chloride  ion \\ NO_3  ^- & Nitrate  ion \end{matrix} \right\} \pmb{Little or no reaction as bases}	Increasing base strength
	\pmb{ Hydronium  ion }           \pmb{ H_3O^+ }	\pmb{ H_2O }                  \pmb{ Water }
	\pmb{Weak  acids} \begin{cases} Hydrogen  & HSO_4  ^- \\       sulfate  ion \\ Phosphoric  acid & H_3PO_4 \\ \\ Nitrous  acid & HNO_2 \\ Hydrofluoric  acid & HF \\ Acetic  acid & CH_3COOH \end{cases}	\left. \begin{matrix} SO_4  ^{2-} & Sulfate  ion \\   \\  H_2PO_4  ^- & Dihydrogen \\ &              phosphate  ion \\ NO_2  ^- & Nitrite  ion \\ F^- & Fluoride  ion \\ CH_3COO^- & Acetate  ion \end{matrix} \right\} \pmb{Very  weak  bases}
	\pmb{Very  weak  acids} \begin{cases} Carbonic  acid & H_2CO_3 \\ Dihydrogen & H_2PO_4  ^- \\    phosphate  ion \\ Ammonium  ion & NH_4  ^+ \\ Hydrocyanic  acid & HCN  \\ Bicarbonate  ion & HCO_3  ^- \\ Hydrogen & HPO_4  ^{2-} \\    phosphate  ion \end{cases}	\left. \begin{matrix} HCO_3  ^- & Bicarbonate  ion \\ HPO_4  ^{2-} & Hydrogen \\ &          phosphate ion \\ NH_3 & Ammonia \\ CN^- & Cyanide  ion \\ CO_3  ^{2- } & Carbonate  ion \\ PO_4  ^{3-} & Phosphate  ion  \\  \end{matrix} \right\} \pmb{Weak  bases}
	\pmb{ Water   }                       \pmb{ H_2O }	\left. \pmb{ OH^- }           \pmb{ Hydroxide ion }      \right\} \pmb{   Strong base}