pH of Polybasic acid buffers

pH of Polybasic acid buffers
Here’s some more examples, determine the answers:
Example 2: Calculate the pH of a solution made up to be
0.10 M in H 2 N(CH 2 ) 6 NH 3 Cl and 0.10 M in H 3 N(CH 2 ) 6 NH 3 Cl 2 .
Answer: pH = pK b2 ˆ pOH = 3.24 Y pH = 10.76
Example 3: Calculate the pH of a solution made up to be
0.50 M in H 2 N(CH 2 ) 2 NH 2 and 0.50 M in H 2 N(CH 2 ) 2 NH 3 Cl .
Answer: pH = pK b1 ˆ pOH = 3.28 Y pH = 10.72
Example 4: Calculate the pH of a solution made up to be
0.35 M in H 2 N(CH 2 ) 3 NH 3 Br and 0.35 M in H 3 N(CH 2 ) 3 NH 3 Br 2 .
Answer: pH = pK b2 ˆ pOH = 4.96 Y pH = 9.04
These are all 1:1 buffer so pH .pK a is OK.