whether the solution of a salt is acidic, basic, or neutral

[Vicky Tong 3E]

I read the textbook on deciding whether the solution of a salt is acidic, basic, or neutral.

The textbook states: "First examine the anion to see whether it is the conjugate base of a weak acid. If the anion is neither acidic nor basic, examine the cation to see whether it is an acidic metal ion or the conjugate acid of a weak base. If one ion is an acid and the other a base, as in NH4F, then the pH is affected by the reactions of both ions with water and both equilibria must be considered."

I don't really understand this, so it would be really helpful if someone can break this down for me (an example would be greatly appreciated)!

[Madysen Ratsek 3L]

Hi Vicky!
Here are the steps I go by when trying to figure out if a salt is acidic, basic, or neutral:
First, identify the cation and anion in a salt, for example, we can use KCl. This can be broken into a K+ and a Cl-.
Now we figure out what compounds each of these ions came from. K+ had to have come from a base, in this case KOH (it helps to write out the equation of the reaction!). Similarly, Cl- comes from HCl. We know KOH is a strong base, and HCl is a strong acid. Knowing this, we can apply the following rule:
Strong acids produce weak bases, and strong bases produce weak acids. So, K+ and Cl- are both considered weak (K+ a weak conjugate acid of KOH, and Cl- a weak conjugate base of HCl).
Knowing that both are weak, neither are going to affect the salt's pH, and KCl is considered a neutral salt. On the other hand, if we had a situation where one of the ions of the salts is a conjugate acid/base of a WEAK base/acid, the CA/CB would be considered strong, and WOULD affect the pH. (See NaCN).
I hope this helps a little!