What is an Acid Base Neutralization Reaction?
An acid base neutralization reaction is when an acid reacts with a base to create water and a salt.
The proton (H+) from the acid combines with the hydroxide (OH–) from the base to make water (H2O). The salt that is formed comes from the acid and base.
This type of reaction is referred to as a neutralization reaction because it neutralizes the acid and base. If a strong acid and strong base react completely (meaning there are equal moles of each), then the resulting solution will have a pH of 7 (neutral).
A neutralization reaction is also a type of double displacement reaction.
What are the products of a neutralization reaction?
The products of a neutralization reaction will always be water (H2O) and a salt. The salt that is formed will depend on the acid and base used. The salt maybe soluble and dissolve in solution, or it could be insoluble and precipitate out of solution.
Strong Acid and Strong Base Neutralization Reaction
The complete neutralization of a strong acid and a strong base happens when there are equal mole amounts of strong acid and strong base. The result is an aqueous solution that has a pH of 7.
There are not very many strong acids and strong bases. Below is a table of all of them.
| Strong Acids | Strong Bases |
| HCl | LiOH |
| HBr | NaOH |
| HI | KOH |
| HNO3 | Ca(OH)2 |
| H2SO4 | RbOH |
| HClO3 | Sr(OH)2 |
| HClO4 | CsOH |
| Ba(OH)2 |
Neutralization with Weak Acid or Weak Base
Reactions with either a weak acid or weak base do not normally result in a pH of 7. Water and salt are still produced.
If the reaction involves a weak acid and a strong base, then the resulting pH will be slightly basic (pH> 7).
When the neutralization reaction involves a strong acid and weak base, then the resulting pH will be slightly acidic (pH < 7).
If both the acid and base are weak then the final pH will be dependent on the pKa of the acid and base. The pH can be acidic, basic, or neutral. These reactions also often do not proceed all the way to completion due to the limited dissociation of the weak acid and weak base.
| Acid Type? | Base Type? | Neutralization pH |
| Strong Acid | Strong Base | pH = 7 |
| Strong Acid | Weak Base | pH < 7 (Acidic) |
| Weak Acid | Strong Base | pH > 7 (Basic) |
| Weak Acid | Weak Base | Depends on pKa and pKb |
Example Problems
Suppose you have a reaction of HCl and NaOH in water. What will the products be? What sort of reaction is this? And what is the net ionic equation?
HCl is a strong acid. NaOH is a strong base. Because both an acid and a base are present, we know we have an acid base neutralization reaction.
The products of a neutralization reaction will always be water and salt. In this case, our salt is NaCl. The sodium ion comes from the strong base and the chloride ion comes from the strong acid.
Next we want to write the net ionic equation (NIE). Several of the species in our reaction are aqueous, so we should be able to simplify our equation. We get our net ionic equation by getting rid of any spectator ions that appear on both sides of the equation. In this case, that is Cl– and Na+.
The result is we have protons (H+) from the acid reaction with hydroxide (OH–) from the base to form water!
Real Life Examples
Cooking commonly uses acid base neutralization reactions! For example, when baking cake you often add bicarbonate (baking soda) as an ingredient. Baking soda is a base. There are also acids in some of the ingredients! Common ones are lemon juice, vinegar, or cream. When the acids and base react while cooking they produce water (as all neutralization reactions do!) and carbon dioxide. The carbon dioxide bubbles are what make the cake (and other baked goods) fluffy and light!
For an experiment you can try at home, check out this experiment by Science is Fun!
