Example 13.10b: Determination of Kb from Equilibrium Concentrations

What is the equilibrium constant for the ionization of the \(\ce{HPO4^2-}\) ion, a weak base:

\(\ce{HPO4^2-(aq)}\)\(\ce{ + }\)\(\ce{H2O(l)}\)\(\ce{<=>}\)\(\ce{H2PO4-(aq)}\)\(\ce{ + }\)\(\ce{OH-(aq)}\)\(\ce{ }\)

In a solution containing a mixture of \(\ce{NaH2PO4}\) and \(\ce{Na2HPO4}\) at \(Failed to interpret math QQQequilibrium, c[OH-] QQQ = 1.3\times 10^{-6}\) M; \(c_{\mathrm{\ce{H2PO4-}}}\)\( = 0.042 \cdot M;\) and \(c_{\mathrm{\ce{HPO4^2-}}}\)\( = 0.341\ \mathrm{M}\).

Think about it...