Solving weak acid equilibrium problems: 1. List the major species in the solution. 2. Choose the species that can produce hydronium (hydrogen ion) and write balanced equations for the reactions. 3. Using the values of the equilibrium constants for the reactions you have written, decide which reaction will dominate at equilibrium in it’s [H+]. 4. Write the mass action expression for the dominant equilibrium. 5. List the intitial concentrations of the species participating in the equilibrium. 6. Define the change needed to achieve equilibrium; that is define “x”. 7. Write the eq. concentrations in terms of “x” and plug them into the mass action expression 8. Solve for “x”; calculate [H3O+] and pH.

What is the pH of a 0.785M sol’n of HNO2(aq)?