Write the equilibria of 0.10 M sodium hydrogen sulfite, and determine whether its pH is greater than or less than 7.
Strategy

First, write the chemical reactions in which the amphoteric species acts as an acid, and the reaction in which it acts as a base. Next, write the expression for the equilibrium constant for each reaction, K_a and K_b. Determine the numerical values of K_a and K_b, and compare them to determine which equilibrium dominates.