2. Please use charge balance and mass balance to prove the [H_{3}O^{+}] of Na_{2}HPO_{3 }(with a formal concentration of *F*)in solution is equal to . (10分) [H_{3}O^{+}] = (*K_{2}* and *K_{3}*_{ }are the dissociation constant of NaH_{2}PO_{3} and Na_{2}HPO_{3})