We’re being asked to calculate the pH of a solution that contains formic acid (HCHO2) and sodium formate (NaCHO2).
A solution that contains a weak acid and its conjugate base is a buffer solution.
The pH of a buffer solution can be determined using the Henderson-Hasselbalch equation.
Solve an equilibrium problem (using an ICE table) to calculate the pH of of each solution:
a solution that is 0.18 M in HCHO2 and 0.13 M in NaCHO2