A) Consider the two statements below. Which of the following best explains (I) and (II)?
(I) the K a of HXO 2 is greater than the K a of HYO 2 , but (II) the K a of HX is less than the K a of
HY
A) (I) X is more electronegative than Y, and (II) the H—X bond is shorter than the H—Y bond
B) (I) X is less electronegative than Y, and (II) the H—X bond is longer than the H—Y bond
C) (I) the H—X bond is weaker than the H—Y bond, and (II) X is more electronegative than Y
D) (I) the H—X bond is stronger than the H—Y bond, and (II) X is less electronegative than Y
B) Calculate the pH of a buffer solution consisting of 0.69 M HA (Ka = 6 x 10-6) and 0.53
M NaA.
[ Select ] ["1", "2", "3", "4"] Which buffer has the lowest pH?
[ Select ] ["3", "1", "2", "4"] Which buffer has the greatest capacity?
[ Select ] ["acid", "base"] Should you add a small amount of concentrated
strong acid or strong base to convert sample 1 to sample 4?
Solution
A) Option A) because shorter bond means stronger bond and hence difficult to release H +
and
hence less acidic.
B) pH = p K a + log ( [ A ? ]/ [ HA ] ) = -log(6x10^-6) + log(0.53/0.69)
= -(0.77-6) - 0.114 = 5.116
C) Lease pH means least ratio of [ A ? ]/ [ HA ] which is in Case 2.
Buffer 3 has largest capacity as it has largest amount of salt.

Base beacause acid in sample 4 is less than sample 1