Chapter 4 Section E Neutralization Reactions (2024)

Introductory Chemistry ©David W. Ball Source: Flat World Knowledge

Chapter 4
Section E
Neutralization Reactions

Neutralization Reactions

Learning Objectives

  1. Identify an acid and a base.

  2. Identify a neutralization reaction and predict its products.

Inthe section called “Acids”, we defined an acid as an ionic compound that contains H+as the cation. This is slightly incorrect, but until additional concepts were developed, a betterdefinition needed to wait. Now we can redefine anacid: - An acid isions in an aqueous solution,i.e. any compound that increases the amount of hydrogen ion (H+) in an aqueous solution. The chemical opposite of an acid is a base. The equivalent definition ofa base is that abaseions in an aqueous solution,i.e. any compound that increases the amount of hydroxide ion (OH-) in an aqueous solution. These original definitions were proposed by Arrhenius (the same personwho proposed ion dissociation) in 1884, so they are referred to as theArrhenius definitionof an acid and a base, respectively.

You may recognize that, based on the description of a hydrogen atom, an H+ion is a hydrogen atom that has lost its lone electron; that is, H+is simply a proton. Do we really have bare protons moving about in aqueous solution? No. What ismore likely is that the H+ion has attached itself to one (or more) water molecule(s). To represent this chemically, we definethehydronium ion, a water molecule with an extra hydrogen ion attached to it.as H3O+, which represents an additional proton attached to a water molecule. We use the hydronium ion asthe more logical way a hydrogen ion appears in an aqueous solution, although in many chemicalreactions H+and H3O+are treated equivalently.

The reaction of an acid and a base is called aneutralization reaction. Although acids and bases have their own unique chemistries, the acid and base cancel eachother's chemistry to produce a rather innocuous substance - water. In fact, the general reactionbetween an acid and a base is

acid +base --> water +salt

where the termsaltis generally used to define any ionic compound (soluble or insoluble) that is formed from areaction between an acid and a base. (In chemistry, the wordsaltrefers to more than just table salt.) For example, the balanced chemical equation for the reactionbetween HCl(aq) and KOH(aq) is

HCl(aq) +KOH(aq) --> H2O(l) +KCl(aq)

where the salt is KCl. By counting the number of atoms of each element, we find that only one watermolecule is formed as a product. However, in the reaction between HCl(aq) and Mg(OH)2(aq), additional molecules of HCl and H2O are required to balance the chemical equation:

2HCl(aq) +Mg(OH)2(aq) --> 2H2O(l) +MgCl2(aq)

Here, the salt is MgCl2. (This is one of several reactions that take place when a type of antacid - a base - is used totreat stomach acid.)

Example 11

Write the neutralization reactions between each acid and base.

  1. HNO3(aq) and Ba(OH)2(aq)

  2. H3PO4(aq) and Ca(OH)2(aq)

Solution

See Also
4.7: Acid Base Reactions5.6: Neutralization Reactions7.4: Acid-Base Neutralization7.17: Acids-Bases Reactions- Neutralization

First, we will write the chemical equation with the formulas of the reactants and the expectedproducts; then we will balance the equation.

  1. The expected products are water and barium nitrate, so the initial chemical reaction is

    HNO3(aq) +Ba(OH)2(aq) --> H2O(l) +Ba(NO3)2(aq)

    To balance the equation, we need to realize that there will be two H2O molecules, so two HNO3molecules are required:

    2HNO3(aq) +Ba(OH)2(aq) --> 2H2O(l) +Ba(NO3)2(aq)

    This chemical equation is now balanced.

  2. The expected products are water and calcium phosphate, so the initial chemical equation is

    H3PO4(aq) +Ca(OH)2(aq) --> H2O(l) +Ca3(PO4)2(s)

    According to the solubility rules, Ca3(PO4)2is insoluble, so it has an (s) phase label. To balance this equation, we need two phosphate ionsand three calcium ions; we end up with six water molecules to balance the equation:

    2H3PO4(aq) +3Ca(OH)2(aq) --> 6H2O(l) +Ca3(PO4)2(s)

    This chemical equation is now balanced.

Test Yourself

Write the neutralization reaction between H2SO4(aq) and Sr(OH)2(aq).

Answer

H2SO4(aq) +Sr(OH)2(aq) --> 2H2O(l) +SrSO4(aq)

See Also
Acids, Bases, Neutralization, and Gas-Forming Reactions (M3Q3-4) – UW-Madison Chemistry 103/104 Resource Book

Neutralization reactions are one type of chemical reaction that proceeds even if one reactant isnot in the aqueous phase. For example, the chemical reaction between HCl(aq) and Fe(OH)3(s) still proceeds according to the equation

3HCl(aq) +Fe(OH)3(s) --> 3H2O(l) +FeCl3(aq)

even though Fe(OH)3is not soluble. When one realizes that Fe(OH)3(s) is a component of rust, this explains why some cleaning solutions for rust stains containacids - the neutralization reaction produces products that are soluble and wash away. (Washing withacids like HCl is one way to remove rust and rust stains, but HCl must be used with caution!)

Complete and net ionic reactions for neutralization reactions will depend on whether the reactantsand products are soluble, even if the acid and base react. For example, in the reaction of HCl(aq)and NaOH(aq),

HCl(aq) +NaOH(aq) --> H2O(l) +NaCl(aq)

the complete ionic reaction is

H+(aq) +Cl-(aq) +Na+(aq) +OH-(aq) --> H2O(l) +Na+(aq) +Cl-(aq)

The Na+(aq) and Cl-(aq) ions are spectator ions, so we can remove them to have

H+(aq) + OH-(aq)---> H2O(l)

as the net ionic equation. If we wanted to write this in terms of the hydronium ion, H3O+(aq), we would write it as

H3O+(aq) +OH-(aq) ---> 2H2O(l)

With the exception of the introduction of an extra water molecule, these two net ionic equationsare equivalent.

However, for the reaction between HCl(aq) and Cr(OH)2(s), because chromium(II) hydroxide is insoluble, we cannot separate it into ions for the completeionic equation:

2H+(aq) +2Cl-(aq) +Cr(OH)2(s) ---> 2H2O(l) +Cr2+(aq) +2Cl-(aq)

The chloride ions are the only spectator ions here, so the net ionic equation is

2H+(aq) +Cr(OH)2(s) --> 2H2O(l) +Cr2+(aq)

Example 12

Oxalic acid, H2C2O4(s), and Ca(OH)2(s) react very slowly. What is the net ionic equation between these two substances if the saltformed is insoluble? (The anion in oxalic acid is the oxalate ion, C2O42-.)

Solution

The products of the neutralization reaction will be water and calcium oxalate:

H2C2O4(s) +Ca(OH)2(s) --> 2H2O(l) +CaC2O4(s)

Because nothing is dissolved, there are no substances to separate into ions, so the net ionicequation is the equation of the three solids and one liquid.

Test Yourself

What is the net ionic equation between HNO3(aq) and Ti(OH)4(s)?

Answer

4H+(aq) +Ti(OH)4(s) --> 4H2O(l) +Ti4+(aq)

Key Takeaways

  • The Arrhenius definition of an acid is a substance that increases the amount of H+in an aqueous solution.

  • The Arrhenius definition of a base is a substance that increases the amount of OH-in an aqueous solution.

  • Neutralization is the reaction of an acid and a base, which forms water and a salt.

  • Net ionic equations for neutralization reactions may include solid acids, solid bases, solid salts,and water.

Exercises

1.What is the Arrhenius definition of an acid?
An Arrhenius acid increases the amount of H+ions in an aqueous solution.
2.What is the Arrhenius definition of a base?
An Arrhenius base increases the amount of OH-ions in an aqueous solution.
3.Predict the products of each acid-base combination listed. Assume that a neutralization reactionoccurs.
  1. HCl and KOH
  2. H2SO4and KOH
  3. H3PO4and Ni(OH)2
  1. KCl and H2O
  2. K2SO4and H2O
  3. Ni3(PO4)2and H2O
4.Predict the products of each acid-base combination listed. Assume that a neutralization reactionoccurs.
  1. HBr and Fe(OH)3
  2. HNO2and Al(OH)3
  3. HClO3and Mg(OH)2
  1. FeBr3and H2O
  2. Al(NO2)3and H2O
  3. H2O and Mg(ClO3)2
5.Write a balanced chemical equation for each neutralization reaction in Exercise 3.
  1. HCl +KOH --> KCl +H2O

  2. H2SO4+2KOH --> K2SO4+2H2O

  3. 2H3PO4+3Ni(OH)2--> Ni3(PO4)2+6H2O

6.Write a balanced chemical equation for each neutralization reaction in Exercise 4.
  1. 3HBr +Fe(OH)3--> FeBr3+3H2O

  2. 3HNO2+Al(OH)3--> Al(NO2)3+3H2O

  3. 2HClO3+Mg(OH)2--> Mg(ClO3)2+2H2O

7.Write a balanced chemical equation for the neutralization reaction between each given acid andbase. Include the proper phase labels.
  1. HI(aq) +KOH(aq) ?
  2. H2SO4(aq) +Ba(OH)2(aq) ?
  1. HI(aq) +KOH(aq) --> KI(aq) +H2O(l)
  2. H2SO4(aq) +Ba(OH)2(aq) --> BaSO4(s) +2H2O(l)
8.Write a balanced chemical equation for the neutralization reaction between each given acid andbase. Include the proper phase labels.
  1. HNO3(aq) +Fe(OH)3(s) ?
  2. H3PO4(aq) +CsOH(aq) ?
  1. 3HNO3(aq) +Fe(OH)3(s) --> 3H2O() +Fe(NO3)3(aq)
  2. H3PO4(aq) +3CsOH(aq) --> 3H2O(l) +Cs3PO4(aq)
9.Write the net ionic equation for each neutralization reaction in Exercise 7.
  1. H+(aq) + OH-(aq)--> H2O(l)

  2. 2H+(aq) +SO42(aq) +Ba2+(aq) +2OH-(aq) --> BaSO4(s) +2H2O(l)

10.Write the net ionic equation for each neutralization reaction in Exercise 8.
  1. 3H+(aq) +Fe(OH)3(s) --> 3H2O(l) +Fe3+(aq)

  2. 3H+(aq) +3OH-(aq) -->3H2O(l)

11.Write the complete and net ionic equations for the neutralization reaction between HClO3(aq) and Zn(OH)2(s). Assume the salt is soluble.
Complete ionic equation:2H+(aq) +2ClO3-(aq) +Zn2+(aq) +2OH-(aq) --> Zn2+(aq) +2ClO3-(aq) +2H2O(l)

Net ionic equation:

2H+(aq) +2OH-(aq) -->2H2O(l)
12.Write the complete and net ionic equations for the neutralization reaction between H2C2O4(s) and Sr(OH)2(aq). Assume the salt is insoluble.
Complete ionic equation:H2C2O4(s) +Sr2+(aq) +2OH-(aq) --> SrC2O4(s) +2H2O(l)

Net ionic equation:

H2C2O4(s) +Sr2+(aq) +2OH-(aq) --> SrC2O4(s) +2H2O(l) (There are no spectator ions.)
13.Explain why the net ionic equation for the neutralization reaction between HCl(aq) and KOH(aq) isthe same as the net ionic equation for the neutralization reaction between HNO3(aq) and RbOH.
Because the salts are soluble in both cases, the net ionic reaction is just H+(aq) + OH-(aq) --> H2O(l).
14.Explain why the net ionic equation for the neutralization reaction between HCl(aq) and KOH(aq) isdifferent from the net ionic equation for the neutralization reaction between HCl(aq) and AgOH.
Although in the first neutralization reaction only H2O is formed, in the second neutralization both H2O and solid AgOH are formed.
15.Write the complete and net ionic equations for the neutralization reaction between HCl(aq) andKOH(aq) using the hydronium ion in place of H+. What difference does it make when using the hydronium ion?
Complete ionic equation:H3O+(aq) +Cl-(aq) +K+(aq) +OH-(aq) --> 2H2O(l) +K+(aq) +Cl-(aq)

Net ionic equation:

H3O+(aq) + OH-(aq) --> 2H2O(l)

The difference is simply the presence of an extra water molecule as a product.

16.Write the complete and net ionic equations for the neutralization reaction between HClO3(aq) and Zn(OH)2(s) using the hydronium ion in place of H+. Assume the salt is soluble. What difference does it make when using the hydronium ion?
Complete ionic equation:2H3O+(aq) + ClO3-(aq) +Zn2+(aq) +2OH-(aq) --> 4H2O(l) +Zn2+(aq) +ClO3-(aq)

Net ionic equation:

2H3O+(aq) +2OH-(aq) --> 4H2O(l)

The difference is simply the presence of two extra water molecules as a product.

Preguntas de revisin

Tareas

Quiz

[Your opinion is important to us. If you have a comment, correction or question pertaining to this chapter please send it tocomments@peoi.org .]

Modified: 2013-01-20 Next:
Chapter 4 Section E Neutralization Reactions (2024)
Top Articles
EASY Ladyfingers Recipe - Alyona’s Cooking
7 Best Prop Trading Firms of 2024 Reviewed
Szalone czaszki: 12 niesamowitych czapek z czaszkami
Jak golić nogi: wskazówki dotyczące golenia dla mężczyzn
Latest Posts
Best Options Prop Trading Firms 2024
Best Futures Prop Firms 2024 - ProprietaryFirms.com
Article information

Author: Catherine Tremblay

Last Updated:

Views: 5794

Rating: 4.7 / 5 (67 voted)

Reviews: 82% of readers found this page helpful

Author information

Name: Catherine Tremblay

Birthday: 1999-09-23

Address: Suite 461 73643 Sherril Loaf, Dickinsonland, AZ 47941-2379

Phone: +2678139151039

Job: International Administration Supervisor

Hobby: Dowsing, Snowboarding, Rowing, Beekeeping, Calligraphy, Shooting, Air sports

Introduction: My name is Catherine Tremblay, I am a precious, perfect, tasty, enthusiastic, inexpensive, vast, kind person who loves writing and wants to share my knowledge and understanding with you.