Acid-Base Neutralization Jean Brainard, Ph.D. Say Thanks to the Authors

Acid-Base Neutralization
Jean Brainard, Ph.D.
Say Thanks to the Authors
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Printed: January 3, 2014
AUTHOR
Jean Brainard, Ph.D.
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C ONCEPT
Concept 1. Acid-Base Neutralization
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Acid-Base Neutralization
• Identify the ions produced when acids and bases dissolve in water.
• Describe neutralization reactions and the formation of salts.
What is one of the most important characteristics of a referee? A referee must be neutral. He can’t favor one team
over the other. In chemistry, being neutral means not being an acid or a base. Pure water is an example of a neutral
substance. In some chemical reactions, an acid and a base combine to form neutral products, including water. You’ll
see how this happens when you read this article.
Acids, Bases, and Ions
An acid is a compound that produces positive hydrogen ions (H+ ) and negative nonmetal ions when it dissolves in
water. (Ions are atoms that have become charged by losing or gaining electrons.) Hydrochloric acid (HCl) is an
example of an acid. When it dissolves in water, it produces positive hydrogen ions and negative chloride ions (Cl− ).
This can be represented by the chemical equation:
H O
2
HCl →
H+ + Cl−
A base is a compound that produces negative hydroxide ions (OH− ) and positive metal ions when it dissolves in
water. For example, when the base sodium hydroxide (NaOH) dissolves in water, it produces negative hydroxide
ions and positive sodium ions (Na+ ). This can be represented by the chemical equation:
H O
2
NaOH →
OH− + Na+
Q: If you were to combine acid and base solutions, what products do you think would be produced?
A: Combining acid and base solutions produces water and a neutral ionic compound.
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Reactions of Acids and Bases
When an acid and a base react, the reaction is called a neutralization reaction. That’s because the reaction produces
neutral products. Water is always one product, and a salt is also produced. A salt is 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 → H2 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− → H2 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 the Figure 1.1.
FIGURE 1.1
These antacid tablets contain the base
calcium carbonate (CaCO3 ). 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 (CaCl2 ). Carbon dioxide (CO2 ) is also produced. The
reaction is represented by the chemical equation:
CaCO3 + 2HCl → H2 O + CaCl2 + CO2
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.
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Concept 1. Acid-Base Neutralization
Vocabulary
• neutralization reaction: Reaction of an acid and a base that produces water and a salt, both of which are
neutral in acidity.
• salt: Ionic compound formed when an acid and base react.
Practice
Watch the animated reaction at the following URL, and then answer the questions below.
http://www.mpcfaculty.net/mark_bishop/neutralization.htm
1.
2.
3.
4.
What reaction is modeled in the animation?
When the reactant solutions mix, what four ions are present in the solution?
How do the ions combine to form neutral products?
What is the complete chemical equation for the reaction?
Review
1. Describe a neutralization reaction.
2. What is a salt? Give an example.
3. Fill in the missing products in the chemical equation below. It represents a neutralization reaction between
solutions of nitric acid (HNO3 ) and potassium hydroxide (KOH): HNO3 + KOH → ____ + _____
References
1. User:Midnightcomm/Wikimedia Comons. . CC BY 2.0
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