Question

Write the charge balance for an aqueous solution of arsenic acid, ${\mathbf{H}}_{\mathbf{3}}{\mathbf{AsO}}_{\mathbf{4}}$, in which the acid can disassociate to role="math" localid="1654936423245" ${\mathbf{H}}_{\mathbf{3}}{{\mathbf{AsO}}^{\mathbf{-}}}_{\mathbf{4}}\mathbf{,}\mathbf{H}{{\mathbf{AsO}}_{\mathbf{4}}}^{\mathbf{2}\mathbf{-}}\mathbf{,}\mathbf{}{{\mathbf{andAsO}}_{\mathbf{4}}}^{\mathbf{3}\mathbf{-}}$. Look up the structure of arsenic acid in Appendix G and write the structure of${{\mathbf{HAsO}}^{\mathbf{2}\mathbf{-}}}_{\mathbf{4}}$

Short answer

Thus the charge balance equation for aqueous solution of arsenic acid, ${\mathrm{H}}_3{\mathrm{AsO}}_4$, in which the acid can disassociate to role="math" localid="1654936784437" ${\mathrm{H}}_2{{\mathrm{AsO}}^{-}}_4,{{\mathrm{HAsO}}_4}^{2-},{{\mathrm{andAsO}}_4}^{3-}$ is${\mathrm{H}}^{+}={\mathrm{H}}_2{{\mathrm{AsO}}_4}^{-}+2\left[{{\mathrm{HAsO}}_4}^{2-}\right]+3\left[{{\mathrm{AsO}}_4}^{3-}\right]+{\mathrm{OH}}^{-}$

Step-by-step solution

Step 1:Disassociation of an aqueous solution of Arsenic acid.

In this problem, we are in a need to write the charge balance for an aqueous solution of arsenic acid${\mathrm{H}}_3{\mathrm{AsO}}_4$.

We also need to note that the aqueous solution of arsenic acid can disassociate as follows,

$$\begin{gathered} \mathrm{i}.{\mathrm{H}}_3{\mathrm{AsO}}_4\iff {\mathrm{H}}^{+}+{\mathrm{H}}_2{{\mathrm{AsO}}_4}^{-} \\ \mathrm{ii}.{\mathrm{H}}_3{{\mathrm{AsO}}_4}^{-}\iff {\mathrm{H}}^{+}+\mathrm{H}{{\mathrm{AsO}}_4}^{2-} \\ \mathrm{iii}.{{\mathrm{HAsO}}_4}^{2-}\iff {\mathrm{H}}^{+}+{{\mathrm{AsO}}_4}^{3-} \\ \mathrm{iv}.{\mathrm{H}}_2\mathrm{O}\iff {\mathrm{H}}^{+}+{\mathrm{OH}}^{-} \end{gathered}$$

Step 2:Charge Balance Equation of Arsenic Acid.

The charge balance of the arsenic acid can be written as follows

${\mathrm{H}}^{+}={\mathrm{H}}_2{{\mathrm{AsO}}_4}^{-}+2\left[{{\mathrm{HAsO}}_4}^{2-}\right]+3\left[{{\mathrm{AsO}}_4}^{3-}\right]+{\mathrm{OH}}^{-}$

Thus the charge balance equation for aqueous solution of arsenic acid,${\mathrm{H}}_3{\mathrm{AsO}}_4$, in which the acid can disassociate to ${\mathrm{H}}_2{{\mathrm{AsO}}^{-}}_4,{{\mathrm{HAsO}}_4}^{2-},{{\mathrm{andAsO}}_4}^{3-}$is ${\mathrm{H}}^{+}={\mathrm{H}}_2{{\mathrm{AsO}}_4}^{-}+2\left[{{\mathrm{HAsO}}_4}^{2-}\right]+3\left[{{\mathrm{AsO}}_4}^{3-}\right]+{\mathrm{OH}}^{-}$