Acid base strength rationale

[Kruz87]

Hello everybody, I'm having difficulty understanding the rationalization behind the strengths of Bronstend Lowry acids and bases and my textbook isn't too helpful. Can someone please expalin to me: (1) What exactly is effective negative charge density? (2) how does electronegativiy correspond to negative charge density? (3) How does negative charge density correspond to the strength or stability of the conjugate base of an acid?

 

[chaoseverlasting]

The total negative charge per unit volume of the atom. The higher the electro negativity, the more charge the atom can retain in a lower volume (the more "pull" it has), and hence higher negative charge density.

If the negative charge density of the conjugate base of an acid is lesser, then that species is more stable as it does not attract the positive charges as strongly. Therefore, it has less tendency to attract the positive species just released by the acid (H+) and the reaction tends more towards the forward side. Ie, H2So4, because SO4(2-) is large in volume (Sulfur and Oxygen are bulky) it has lower negative charge density, and this makes H2SO4 more acidic.

The converse is also true for base strength.

 

[Blueshift5]

Hello,

I would be happy to provide some clarification on the concepts of acid base strength and effective negative charge density.

(1) Effective negative charge density refers to the distribution of negative charge within a molecule or ion. This is influenced by the electronegativity of the atoms involved and their spatial arrangement. The more concentrated the negative charge is in a particular area, the higher the effective negative charge density will be.

(2) Electronegativity is a measure of an atom's ability to attract electrons towards itself in a chemical bond. This means that atoms with higher electronegativity will have a stronger pull on electrons, resulting in a higher effective negative charge density.

(3) The negative charge density of a conjugate base is directly related to its stability. A more stable conjugate base will have a higher effective negative charge density, as the negative charge is distributed more evenly and is less likely to be attracted by other positively charged species. This stability is also reflected in the strength of the acid, as a stronger acid will have a more stable conjugate base.

I hope this helps to clarify the concepts of effective negative charge density and its relationship to acid base strength. If you have any further questions, please don't hesitate to ask.