Question

Calculate the change in pH that occurs when 0.00100 mol of gaseous HCl is added to a buffer solution that is prepared by dissolving 4.92 g of sodium acetate ( molar mass= 82.03 g/mol) in 250 mL of 0.150 mol/L of acetic acid solution? Assume no change in volume upon addition of either the sodium acetate or HCl. (Ka for acetic acid = 1.8x10^-5) *please explain!*