What is the pH of 0.01 M glycine solution? For glycine `K_(a_(1)) = 4.5 xx 10^(-3)` and `Ka_(2) = 1.7 xx 10^(-10)` at 298 K

Options

A. `3.0`
B. `10.0`
C. 6.1
D. 7.2

Answer

To find the pH of a 0.01 M glycine solution, we can use the given values of the dissociation constants \( K_{a1} \) and \( K_{a2} \).

### Step 1: Calculate \( pK_{a1} \) and \( pK_{a2} \)

The dissociation constants are given as:
- \( K_{a1} = 4.5 \times 10^{-3} \)
- \( K_{a2} = 1.7 \times 10^{-10} \)

We can calculate \( pK_a \) using the formula:
\[ pK_a = -\log(K_a) \]

**For \( K_{a1} \):**
\[ pK_{a1} = -\log(4.5 \times 10^{-3}) \approx 2.35 \]

**For \( K_{a2} \):**
\[ pK_{a2} = -\log(1.7 \times 10^{-10}) \approx 9.77 \]

### Step 2: Calculate the average of \( pK_{a1} \) and \( pK_{a2} \)

To find the pH of the glycine solution, we can use the average of \( pK_{a1} \) and \( pK_{a2} \):
\[ pH = \frac{pK_{a1} + pK_{a2}}{2} \]

Substituting the values we calculated:
\[ pH = \frac{2.35 + 9.77}{2} = \frac{12.12}{2} = 6.06 \]

### Conclusion

Thus, the pH of the 0.01 M glycine solution is approximately **6.06**.

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