Which of the following is the major solute species in a solution of glutamic acid at pH=1.3?

Options

A.
B.
C.
D.

Answer

To determine the major solute species in a solution of glutamic acid at pH 1.3, we need to analyze the behavior of glutamic acid in acidic conditions.

### Step-by-step Solution:

1. **Understanding Glutamic Acid Structure**:
Glutamic acid is an amino acid with the following functional groups:
- An amino group (-NH2)
- Two carboxylic acid groups (-COOH)

2. **Identifying the pH**:
The given pH of the solution is 1.3, which indicates that the solution is highly acidic.

3. **Behavior of Amino Acids at Different pH Levels**:
- At low pH (acidic conditions), amino acids tend to gain protons (H+).
- The amino group (-NH2) can accept a proton to become -NH3+.
- The carboxylic acid groups (-COOH) are already in their protonated form and will not lose any protons in acidic conditions.

4. **Zwitterion Formation**:
- At the isoelectric point (pI), amino acids exist as zwitterions, where the amino group is protonated (-NH3+) and one of the carboxylic groups is deprotonated (-COO-).
- However, at pH 1.3, which is much lower than the pI of glutamic acid, the amino group will be fully protonated, and both carboxylic groups will remain protonated.

5. **Conclusion**:
At pH 1.3, the major species of glutamic acid will be the fully protonated form, which can be represented as:
- NH3+ - CH(COOH) - CH2 - COOH
This indicates that both carboxylic acid groups are protonated, and the amino group is also protonated.

### Final Answer:
The major solute species in a solution of glutamic acid at pH 1.3 is the fully protonated form of glutamic acid, represented as NH3+ - CH(COOH) - CH2 - COOH.

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