An acid-base reaction or a neutralization reaction is a <u>chemical reaction that occurs between an acid and a base producing a salt and water</u>. The acids and bases can be strong or weak depending on their degree of ionization in water.
Butyric acid is a weak acid and in water it is ionized in the following way, loosing a proton (H+):
HC4H7O2 (aq) ⇆ H+ (aq) + C4H7O2- (aq)
On the other hand, potassium hydroxide is a strong base, so it will be completely ionized in water:
KOH(aq) → K+(aq) + OH-(aq)
Then the <u>net acid-base reaction</u> between butyric acid and KOH is:
HC4H7O2 (aq) + OH- (aq) ⇆ H2O + C4H7O2- (aq)
It is valid to consider only the OH- produced from the ionization of KOH in water since, as mentioned, this molecule is completely ionized. Also, we do not include the K + in the net equation since it is a spectator ion, it does not undergo chemical changes.