Why isn't acetic acid a strong electrolyte/acid

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In summary: Yes, it is possible to use the Botzmann distribution to compute the molar energy difference, e.g. \Delta E= E_{Ac^-}-E_{AcH}=-RT\ln\frac{[Ac^-]}{[AcH]}in a solution of acetic acid.
  • #1
gsingh2011
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Since HC2H3O2 is made up of acetate which is a polyatomic ion, shouldn't it ionically bond with H+? If that's the case, why doesn't it completely dissociate in water and become a strong electrolyte?
 
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  • #2
gsingh2011 said:
Since HC2H3O2 is made up of acetate which is a polyatomic ion, shouldn't it ionically bond with H+?

Just because something is polyatomic doesn't mean it is ionic.

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  • #3
The degree of covalent vs. ionic nature of a bond is determined by the difference in electronegativity of the bonding atoms. In the case of O and H, you get a polar covalent bond, not an ionic one.
 
  • #4
espen180 said:
The degree of covalent vs. ionic nature of a bond is determined by the difference in electronegativity of the bonding atoms. In the case of O and H, you get a polar covalent bond, not an ionic one.

This is actually a little bit more complicated in the case of carboxylic acids - this is not just a common O-H bond like in alcohol, as there is a carbonyl group close by, which stabilizes anion after dissociation. Still, you are right that it is not an ionic bond.

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  • #5
Yes, that's true. The nearby carbonyl group does contribute to the ionic nature of the O-H bond in a carboxyl group. Resonance stabilization is the reason they dissociate to the degree they do. The point is that the degree of ionic character of the bond is not the sole factor determining solubility. For example, compare the dissociation constants of ethanol and sulfuric acid.
 
  • #6
Acetic acid is a weak acid because acetate and a free proton are not as thermodynamically stable as acetic acid.

Consider the acid dissociation constant (K_a): an acid with a low K_a, has an equilibrium concentration of the acid that is much greater than the product of the equilibrium concentration of the conjugate base and the equilibrium concentration of protons.

Strong acids completely dissociate; therefore, they have very large K_a's.
 
  • #7
You might say it is thermodynamic instability. I would say it is due to the difference in energy. Maybe it's the same thing?

Is it possible to use the Botzmann distribution to compute the molar energy difference, e.g.
[tex]\Delta E= E_{Ac^-}-E_{AcH}=-RT\ln\frac{[Ac^-]}{[AcH]}[/tex]
in a solution of acetic acid?
 

1. Why does acetic acid have a lower conductivity compared to other strong acids?

Acetic acid is a weak acid, meaning it does not completely dissociate into ions in solution. This results in a lower concentration of ions, which are responsible for conducting electricity. In contrast, strong acids, such as hydrochloric acid, fully dissociate into ions, resulting in a higher concentration of ions and thus higher conductivity.

2. How does the molecular structure of acetic acid affect its strength as an electrolyte?

The molecular structure of acetic acid is characterized by a carboxylic acid functional group (-COOH) attached to a methyl group (-CH3). This structure makes it difficult for acetic acid molecules to dissociate into ions in solution, resulting in a weaker electrolyte compared to acids with simpler molecular structures.

3. Can acetic acid ever be a strong electrolyte?

No, acetic acid will always be a weak electrolyte due to its molecular structure. However, its strength as an electrolyte can be increased by adding a strong acid or base, which will help to further dissociate acetic acid molecules into ions.

4. How does the concentration of acetic acid affect its strength as an electrolyte?

The concentration of acetic acid does not affect its strength as an electrolyte, as it is a weak acid and will not fully dissociate into ions regardless of its concentration. However, a higher concentration of acetic acid will result in a higher conductivity due to a higher number of ions present in solution.

5. Why is acetic acid considered a weak acid despite its sour taste and ability to dissolve some metals?

Acetic acid may taste sour and have some corrosive properties, but this does not necessarily make it a strong acid. Its ability to dissolve some metals is due to its acidic nature, but this does not mean it fully dissociates into ions. Acetic acid is still classified as a weak acid due to its low dissociation constant and lower conductivity compared to strong acids.

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