A buffer solution is formed by adding 0.200 moles of solid potassium nitrite, KNO2 to 500.0 ml of 0.500 M nitrous acid, HNO2 solution. You may assume that the change in volume is negligible upon addition of the solid. Calculate the pH of the buffer solution. pH= Calculate the pH of the buffer solution after the addition of 5.00 ml of 4.00 M HNO3. pH = Check