(I) X is more electronegative than Y, making the H-X bond shorter and stronger than the H-Y bond. Therefore, HXO2 is more acidic than HYO2. (II) The stronger H-X bond means HX is less acidic than HY. The pH of the buffer solution is 5.116. Buffer 2 would have the lowest pH because it has the lowest ratio of [A-]/[HA]. Buffer 3 has the greatest capacity because it contains the largest total amount of the salt. Strong base should be added to convert sample 1 to sample 4 because sample 4 contains less acid.