We are being asked to find pKb of the ascorbate ion. Recall that pKb can be calculate from Kb using the following equation:
However, we're given the Ka for ascorbic acid (HC6H7O6 , vitamin C). Ascorbate ion is the conjugate base of ascorbic acid.
HC6H7O6 + H2O ⇌ C6H7O6- + H3O+
(weak acid) (base) (conjugate base) (conjugate acid)
Hence, the Kb of C6H7O6- can be calculated from the Ka of HC6H7O6. Ka and Kb are connected by the autoionization constant of water (Kw) in the following equation:
The value of Ka at 25 °C for ascorbic acid (HC6H7O6 , vitamin C), is 8.0 × 10–5. What is pKb of the ascorbate ion?
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