Final answer:
At pH 9.0, glycine is above its isoelectric point and predominantly exists in an anionic form with its carboxyl group deprotonated and amino group protonated, indicating that it is partially ionized.
Step-by-step explanation:
The question addresses the ionization state of glycine in a 0.1 M solution at pH 9.0. To understand the answer, one should know that glycine, like other amino acids, can act as both an acid and a base. It has an amino group (-NH3+), which can donate a proton, and a carboxyl group (-COOH), which can accept a proton. At a pH lower than its isoelectric point ((pI)), the amino group is protonated, and the molecule carries a net positive charge. Conversely, at a pH higher than the pI, the carboxyl group is deprotonated, and the molecule carries a net negative charge. The pI of glycine is around 6. At pH 9.0, glycine is above its pI, leading to deprotonation of the carboxyl group, while the amino group remains with a proton, hence the molecule mostly exists in its anionic form (carboxylate ion, -COO-, and protonated amino group, -NH3+). Therefore, at pH 9.0, glycine is not fully ionized, but it is predominantly in the anionic form due to the deprotonated carboxyl group, so the correct answer is B) Glycine is partially ionized.