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I know that according to Brönsted-Lowry theory, a base is a proton acceptor while an acid is a proton donor. Also, the acid-base pair that differs by a single proton is a conjugate pair.

If this is true, then the sodium ion is a conjugate acid of sodium hydroxide. But if we look at $\ce{Na^+}$ itself, we find that it cannot donate a proton. Someone in the comments under this answer suggested that in its hydrated state, $\ce{Na^+}$ can act as a Brönsted-Lowry acid. How?

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  • $\begingroup$ Not a duplicate of this question which is the one about which I seek clarification. $\endgroup$ – Ray Bradbury Jan 4 at 15:49
  • $\begingroup$ Why the downvote? $\endgroup$ – Ray Bradbury Jan 4 at 15:52
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    $\begingroup$ " sodium ion is a conjugate acid of sodium hydroxide" - it is not. Protonate NaOH molecule and you'll find it. $\endgroup$ – Mithoron Jan 4 at 18:44
  • $\begingroup$ @Mithoron I think I get it. As I understand it, and as someone else wrote on this SE, writing NaOH (aq) is really writing Na+ (aq) + OH- (aq). Protonating OH- gives H20, which is the conjugate acid, not Na+. In sum, is sodium ion not a Brönsted-Lowry acid? $\endgroup$ – Ray Bradbury Jan 5 at 15:05
  • $\begingroup$ It is an aqua complex and has been so for quite a while now. $\endgroup$ – Jan Jan 19 at 8:59

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