Why do LiOH is weak base as compared to NaOH even though it's hydration enthalpy is greater than Na?
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2$\begingroup$ 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. $\endgroup$ – getafix Mar 22 '16 at 12:37
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$\begingroup$ link.aip.org/link/?JCPSA6/122/194509/1 $\endgroup$ – 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.
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$\begingroup$ I'm confused Wikipedia has pKb as -0.63 for LiOH en.wikipedia.org/wiki/Lithium_hydroxide and a has pKb of +0.2 for NaOH. en.wikipedia.org/wiki/Sodium_hydroxide So isn't LiOH a stronger base?!? $\endgroup$ – MaxW Mar 22 '16 at 17:44
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