Q$3$: Calculate the relative abundance of different carbonate species in water at STP as a function of $pH.$ You may ignore $C{O}_2$ and just calculate that for $H_{2}C{O}_3,HC{O}_3,$ and $C{O}_3^{2-}.$ Using Excel, plot the results on a graph of abundance $(0$ to $100\%)$ vs pH $(0$ to $14$ in $0\mathrm{.}5$ intervals$).$ The total dissolved carbonate species is ${10}^{-3}mol{L}^{-1}.$

$($Hint; in our homework we plotted the concentration of each As species as a function of pH$.$ This current question asks you to plot the abundance of each species. Use pKa$1=6\mathrm{.}35$ and pKa$2=10\mathrm{.}3.$

Q$4$: Plot the buffering capacity $($on log scale$)$ as a function of $pH(1$ to $14$ in $0\mathrm{.}5$ intervals$),$ for an aqueous solution containing $1{10}^{-2}mol{L}^{-1}$ silicic acid at $25C.$ Assume that only the first two dissociation steps are significant. The pKa$1=9\mathrm{.}83$ and pKa$2=13\mathrm{.}17.$