Question

A 1.0 L buffer solution contains 0.100 mol HC2H3O2 and 0.100 mol NaC2H3O2. The value of Ka for HC2H3O2 is 1.8x10^-5. Calculate the pH of the solution upon the addition of 10.0 mL of 1.00 M HCl to the original buffer. Express the your answer to two decimal places.