What does the term buffer solution mean?
Write equations to show how the hydrogencarbonate ion, HCO$_3^-$, regulates the pH of blood.
A mixture containing both Na$_2$HPO$_4$ and NaH$_2$PO$_4$ is often used as a buffer solution. The equilibrium below is established in the solution. H$_2$PO$_4^-$(aq) $\rightleftharpoons$ HPO$_4^{2-}$(aq) + H$^+$(aq) \quad $K_a = 6.2 \times 10^{-8}$ mol dm$^{-3}$ Calculate the pH of a buffer solution prepared by mixing 100 cm$^3$ of 0.5 mol dm$^{-3}$ Na$_2$HPO$_4$ and 100 cm$^3$ of 0.3 mol dm$^{-3}$ NaH$_2$PO$_4$.
Silver phosphate, Ag$_3$PO$_4$, dissolves only slightly in water. Write an expression for the solubility product, $K_{sp}$, of Ag$_3$PO$_4$, and give its units.
The value of $K_{sp}$ is $1.25 \times 10^{-20}$ at 298 K. Use this to calculate [Ag$^+$(aq)] in a saturated solution of Ag$_3$PO$_4$.
The half-equation for the redox reaction between phosphoric(III) acid and phosphoric(V) acid is shown. H$_3$PO$_4$(aq) + 2H$^+$(aq) + 2e$^- \rightleftharpoons$ H$_3$PO$_3$(aq) + H$_2$O(l) \quad $E^\circ = -0.28$ V Use suitable information from the Data Booklet to write an equation for the reaction between H$_3$PO$_3$ and Fe$^{3+}$(aq) ions, and calculate the $E^\circ_{\text{cell}}$ for the reaction.