How does electronegativity affect acidity?

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How does electronegativity affect acidity?

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Answer 1 · 2017-08-28T16:34:08

The strength of an acid is given by the extent of the following equilibrium.......

Explanation:

$H X + H_{2} O ⇌ H_{3} O^{+} + X^{-}$ $HX + H_2O rightleftharpoonsH_3O^+ + X^-$

Now for the hydrogen halides, the more ELECTRONEGATIVE the halide, the WEAKER the acid, i.e. for $H F$ $HF$ , significant amounts of $H F$ $HF$ remain undissociated, and when a fluoride salt, say $N a F$ $NaF$ , is dissolved in water, the solution is ALKALINE given the following equilibrium.....

$F^{-} + H_{2} O ⇌ H F + H O^{-}$ $F^(-) + H_2O rightleftharpoons HF + HO^-$

For $H C l$ $HCl$ , $H B r$ $HBr$ , and $H I$ $HI$ , because the conjugate base is larger, and more diffuse, and LESS charge-dense, the equilibrium lies almost entirely to the right.......

$H X + H_{2} O \to H_{3} O^{+} + X^{-}$ $HX +H_2OrarrH_3O^+ + X^-$ , $X = C l, B r, I, \neq F$ $X=Cl, Br, I, !=F$

So in this (special!) instance, electronegativity militates against acidity. Of course, here, an entropy effect also is important, in that the $F^{-}$ $F^-$ ion is entropically disfavoured.

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How does electronegativity affect acidity?

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