Final answer:
To calculate the pH of a 0.75 M potassium formate solution, determine the dissociation constant (Ka) for formic acid and set up an equilibrium expression to find the OH- concentration. Then calculate pOH and use the relationship pH + pOH = 14 to find the pH.
Step-by-step explanation:
To calculate the pH of potassium formate solution (HCOOK), we must consider it as a salt derived from a weak acid (formic acid, HCOOH) and a strong base (KOH). Potassium formate dissociates in water to form formate ions (HCOO-) and potassium ions (K+). The formate ion, being the conjugate base of formic acid, will react with water to re-establish equilibrium, accepting protons and generating hydroxide ions (OH-).
To find the pH, we will use the acid dissociation constant (Ka) for formic acid. Looking at similar problems, we see that the pKa is usually given, and is around 3.75. The Ka can be calculated as Ka = 10-pKa = 10-3.75.
From here, we need to set up an equilibrium expression to solve for the concentration of OH- produced and subsequently calculate pOH. Finally, we use the relationship pH + pOH = 14 to find the pH. Without the exact Ka value for formic acid at our disposal, we can't proceed with the calculations, but the student should use their given Ka to solve for the pH of the solution following the steps outlined.