Acid-Base Neutralization Jean Brainard, Ph.D. Say Thanks to the Authors Click http://www.ck12.org/saythanks (No sign in required) To access a customizable version of this book, as well as other interactive content, visit www.ck12.org CK-12 Foundation is a non-profit organization with a mission to reduce the cost of textbook materials for the K-12 market both in the U.S. and worldwide. Using an open-content, web-based collaborative model termed the FlexBook®, CK-12 intends to pioneer the generation and distribution of high-quality educational content that will serve both as core text as well as provide an adaptive environment for learning, powered through the FlexBook Platform®. Copyright © 2014 CK-12 Foundation, www.ck12.org The names “CK-12” and “CK12” and associated logos and the terms “FlexBook®” and “FlexBook Platform®” (collectively “CK-12 Marks”) are trademarks and service marks of CK-12 Foundation and are protected by federal, state, and international laws. Any form of reproduction of this book in any format or medium, in whole or in sections must include the referral attribution link http://www.ck12.org/saythanks (placed in a visible location) in addition to the following terms. Except as otherwise noted, all CK-12 Content (including CK-12 Curriculum Material) is made available to Users in accordance with the Creative Commons Attribution-Non-Commercial 3.0 Unported (CC BY-NC 3.0) License (http://creativecommons.org/ licenses/by-nc/3.0/), as amended and updated by Creative Commons from time to time (the “CC License”), which is incorporated herein by this reference. Complete terms can be found at http://www.ck12.org/terms. Printed: January 3, 2014 AUTHOR Jean Brainard, Ph.D. www.ck12.org C ONCEPT Concept 1. Acid-Base Neutralization 1 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. 1 www.ck12.org 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. 2 www.ck12.org 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 3