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Why do LiOH is weak base as compared to NaOH even though it's hydration enthalpy is greater than Na?

Lighthart
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JM97
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    Well, besides hydration energy, there's other factors at play. How do their lattice energies compare? Look them up, maybe that'll help you answer your own question. – getafix Mar 22 '16 at 12:37
  • http://link.aip.org/link/?JCPSA6/122/194509/1 – Lighthart Mar 22 '16 at 21:40

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$\ce{NaOH}$ and $\ce{LiOH}$ are both classified as ionic compounds, but as with most things in chemistry, this is always on a continuum scale, in this case between ionic and covalent bonds. $\ce{NaOH}$ is 'more' ionic in character which means its $\ce{OH^-}$ is more frequently unaccompanied by its counter cation, $\ce{Na+}$ as compared to $\ce{LiOH}$ and its corresponding $\ce{Li+}$.

Without the cation to balance the character, $\ce{OH^-}$ will balance its charge via deprotonation, and hence it is a stronger base.

Lighthart
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  • I'm confused Wikipedia has pKb as -0.63 for LiOH https://en.wikipedia.org/wiki/Lithium_hydroxide and a has pKb of +0.2 for NaOH. https://en.wikipedia.org/wiki/Sodium_hydroxide So isn't LiOH a stronger base?!? – MaxW Mar 22 '16 at 17:44
  • See link above. – Lighthart Mar 22 '16 at 21:40