Why are more polarized bonds weaker (Acid dissociation)?

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In summary, the weak acidity of dilute hydrofluoric acid is due to the high H-F bond strength, which overcomes the more negative enthalpy of hydration of the fluoride ion. This is often attributed to the high dissolution enthalpy of HF. However, when considering the dissociation of acids, the argument that H-F bond is stronger than H-I bond based on bond enthalpies may be inaccurate. This is because the hydration of ions must also be taken into account. In carboxylic acids, the polarity of O-H bonds is related to their strength, with electron donating groups causing the bond to be less polar and therefore stronger. This is known as the inductive effect.
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yucheng
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Wikipedia says that:
The weak acidity in dilute solution is sometimes attributed to the high H—F bond strength, which combines with the high dissolution enthalpy of HF to outweigh the more negative enthalpy of hydration of the fluoride ion.
(https://en.wikipedia.org/wiki/Hydrofluoric_acid)
(the H-F bond is highly polar compared to the H-I bond)
(H-F bond is stronger than H-I bond)

It is a common argument to say that H-F bond is stronger than H-I bond on the basis of bond enthalpies:

$$\text{HX} -> \text{H(g)} + \text{X(g)}$$.

However, for dissociation of acids, we must actually consider (hence the electron affinity comes in)

$$\text{HX} -> \text{H}^+(g) + \text{X}^-(g)$$,

and then the hydration of the ions, no? Does this mean the argument given above is... inaccurate, though it works?
____________
For O-H bonds in carboxylic acids, electron donating group causes the O-H bond to be less polar hence stronger.
Carboxylic acids, https://en.wikipedia.org/wiki/Inductive_effect

Why Is polarity related to bond strength? Why are polar bonds weaker than non-polar bonds?
 
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  • #2
Polar bonds are weaker than non-polar bonds because the electrons in polar bonds are not evenly distributed. In a non-polar bond, the electrons are shared equally between the two atoms, creating a uniform electric field. In a polar bond, the electrons are attracted to one atom more than the other, causing an unequal distribution of charge and therefore an uneven electric field. This uneven electric field creates an instability, resulting in a weaker bond.
 

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