Problem- A buffer is prepared by mixing 0.25 mols of NaNO2 and 0.75 mols of HNO2 in 1.0 L of water. Calculate the pH of the solution after addition of 0.20 mols of KOH. The Ka for HNO2 is 4.3 x 10^-4.
Please provide step by step instructions as well as preferably solved through ICE chart method rather than Henderson-Hasselbach Equation.