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NEET levelSingle correct optionDifficulty 1 of 3ia166

Sodium hydrogencarbonate is amphiprotic. For $H X_{2} CO X_{3}$ , $p K_{a 1} = 6.4$ and $p K_{a 2} = 10.2$ . Taking the pH of an amphiprotic salt solution as $\frac{1}{2} (p K_{a 1} + p K_{a 2})$ , the pH of an aqueous $NaHCO X_{3}$ solution is

A $7.0$
B $8.3$
C $10.2$
D $6.4$

Answer: B

For an amphiprotic anion,

[H X^{+}] = K_{a 1} K_{a 2}

, so

pH = \frac{1}{2} (6.4 + 10.2) = 8.3

.

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