Salts

[Albert Chen 1G]

How do you determine if a Salt is acidic, basic, or neutral? Which factors do you look at?

1. K2SO3
2. KCl

[005801694]

Look at the ions (cations and anions) that make up the salt when it's ionized. A salt is neutral if there is a cation of the strong base and anion of the strong acid. It is basic if: cation of strong base, anion of weak acid. It's acidic if there's an anion of a strong acid and cation of a weak base. You should probably memorize the common strong acids and bases so that you can recognize when the ions come from them. Hope this helps!

[Jack Amos 2I]

This one tripped me up as well because at first it isn't that obvious, but the key here is that we have to look at these salts as if they were dissociated in water. So for the salts you presented, in water, they would dissociate into:

1. K+ and SO3 2-
2. K+ and Cl-

Through experiment, we have discovered that K+ and Cl- ions really like to stay dissociated in water and won't reform bonds with OH- ions (for K+, since it is a cation) and H+ protons (for Cl-, since it is an anion). Due to this likely irreversibility, there will be a higher concentration of either OH- ions or H+.

For KCl however, since the presence of a strong base cation and a strong acid anion are both apparent, this salt would lead to a neutral solution.
For K2SO3, we know K+ is a cation of a strong base, so there will be a relatively higher concentration of OH- ions. SO3 2- is not an anion of a strong acid, so H+ ions will frequently dissociate and associate with the SO3 2- anion, leaving the concentration of OH- ions higher in a solution of dissolved K2SO3, meaning the solution tends to be basic.

[Sohan Talluri 1L]

There are a lot of factors to consider, but here are some guidelines:
Cations from groups 1 and 2 and Cl-, Br-, and I- from group 17 don't affect pH.
A salt containing an acid will be acidic (ex: NH₄Cl).
A salt containing a base (or the conjugate base of a weak acid) will be basic (ex: NaCH₃CO₂).

For #1, K₂SO₃ dissociates into 2K+ and SO₃^2-. The cation K+ is from group 1, so it doesn't affect the pH. The anion SO₃^2- is the conjugate base of a weak acid, H₂SO₃, so it makes the salt basic.

For #2, KCl dissociates into K+ and Cl-. The cation K+ is from group 1 and the anion Cl- is from group 17, so neither will affect the pH and the salt will be neutral.

Hopefully this helps and please correct me if there are any mistakes.