Buffer (HclO + NaClO) + HCl; pH == ?

Question

A buffer solution is prepared by mixing 600.0 ml of 0.600 M HClO and 400.0 ml of 1.00 M NaClO. Calculate the pH of the solution after 40.0 ml of 3.00 M HCl is added to the buffer. For HClO, Ka = 3.0X 10^-8.

To do this I determined the concentration of H+ before the HCl was added and assumed that the H+ of HCl would join the excess ClO in the solution, thus making a negligible effect on the pH (the excess H+ of the HCl would be used up). My final answer was pH = 4.936

Answer 1

Correct.