Question

A buffer iscreated by dissolving 0.450mol of sodium ascorbate(NaC6H7O6)and 0.500mol of ascorbic acid(HC6H7O6)in enough water to create 1.00Lof solution.. a) what is the original pH of the buffer

Answer 1

Question #77208, Chemistry / Other

A buffer is created by dissolving 0.450 mol of sodium ascorbate (NaC₆H₇O₆) and 0.500 mol of ascorbic acid (HC₆H₇O₆) in enough water to create 1.00 L of solution.. a) what is the original pH of the buffer

Solution:

Henderson–Hasselbalch equation:

$$pH = pK_a + \log \frac{[A^-]}{[HA]}$$ $$[A^-] = \frac{n(A^-)}{V(solution)} = \frac{0.500\ mol}{1.00\ L} = 0.500\ \frac{mol}{L}$$ $$[HA] = \frac{n(HA)}{V(solution)} = \frac{0.450\ mol}{1.00\ L} = 0.450\ \frac{mol}{L}$$

pKa (first) for ascorbic acid is 4.10.

Using values:

$$pH = 4.10 + \log \frac{0.500\ \frac{mol}{L}}{0.450\ \frac{mol}{L}} = 4.10 + 0.05 = 4.15$$

Answer:

4.15

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