K2HPO4 and KH2PO4
The acid is the one with more H atoms; the base is the one with the fewer H atoms. So KH2PO4 is the acid and K2HPO4 is the base. The equilibrium is
H2PO4^- + OH^- ==> HPO42- when strong base is added and
HPO4^2- + H^+ ==> H2PO4^- when strong acid is added.
A buffer consisting of H2PO4- and HPO42-, helps control the pH of physiological fluids. Many carbonated soft drinks also use this buffer system. You were asked to prepare this buffer from K2HPO4 and KH2PO4. Identify the week acid and base components of this buffer solution and justify your choice.
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