CK-12 Physical Science Concepts - For Middle School

3.55 Acid-Base Neutralization

Reactions of Acids and Bases

When an acid and a base react, the reaction is called aneutralization reaction. That’s because the reaction produces
neutral products. Water is always one product, and a salt is also produced. Asaltis a neutral ionic compound. You
can learn more about salts and how they form at this URL: http://www.youtube.com/watch?v=zjIVJh4JLNo.

Let’s see how a neutralization reaction produces both water and a salt, using as an example the reaction between
solutions of hydrochloric acid and sodium hydroxide. The overall equation for this reaction is:

NaOH + HCl→H 2 O and NaCl

Now let’s break this reaction down into two parts to see how each product forms.

• Positive hydrogen ions from HCl and negative hydroxide ions from NaOH combine to form water. This part
  of the reaction can be represented by the equation:

H++ OH−→H 2 O

• Positive sodium ions from NaOH and negative chloride ions from HCL combine to form the salt sodium
  chloride (NaCl), commonly called table salt. This part of the reaction can be represented by the equation:

Na++ Cl−→NaCl

Another example of a neutralization reaction can be seen in theFigure3.104.

FIGURE 3.104

These antacid tablets contain the base

calcium carbonate (CaCO 3 ). The base

reacts with hydrochloric acid (HCl) in the

stomach. The reaction neutralizes the

acid to relieve acid indigestion.

Q:What products are produced when antacid tablets react with hydrochloric acid in the stomach?

A:The products are water and the salt calcium chloride (CaCl 2 ). Carbon dioxide (CO 2 ) is also produced. The
reaction is represented by the chemical equation:

CaCO 3 + 2HCl→H 2 O + CaCl 2 + CO 2

Summary

• When acid and base solutions react, they produce water and a neutral ionic compound called a salt. The
  reaction is called a neutralization reaction.