KBr

[Meachelle_Lum_1I]

Why is KBr neutral when dissolved in water, but KF is not?
For 6th edition 12.65, how can we tell by looking at the salt, if it will release H+ or OH- in water?
salts:
AlCl3
Cu(NO3)2

[Andre_Galenchik_2L]

It may be because bromine is a bigger element than fluorine.

[harshitasarambale4I]

Since bromine is bigger than fluorine, the bond length is going to be longer and weaker. This means it will be a stronger acid.

[Parth Mungra]

The above answers are correct; bromine is bigger, therefore forming a smaller, weaker bond, allowing the bond to be broken easier.
For the salt part of your question: If you have NH4+, for example, this will give a proton (an H+) because then it can form to a NH3. This extra proton will then form a hydronium ion when it is dissolved in water

[dgerges 4H]

"KBr dissociates into K+ and Br-. Br- reacts to make HBr, a strong acid. Since Br- is the conjugate base of HBr, it is weak. K+ is also weak so the two weak components sort of offset and have no real effect on the pH, making it neutral."

[Catherine Kim 3K]

Br is below F on the periodic table, so it is bigger.