Solution to Study Question 4:
This problem is very similar to problem #2, except that you are dealing with an amphoteric molecule. Therefore, there are two acid-base equations to consider. For the amine group, the H:B form will be the ionized form, while the B: form is neutral. For the phenolic group, the opposite is true, and B: is the ionized form. The equation is used in the same way as for question 2.
Sometimes you may want to know the proportion in which both groups are ionized or unionized. This can be done simply by multiplying the fractions of each group ionized or unionized, as determined above. Make sure you do not multiply percents, as you will get the wrong answer. Note that the four percent values you determined in this question, which account for all 4 possible ionization states of morphine, add up to 100%, give or take a bit of rounding error.
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