Chemical Equations Part 1A Directed Learning Activity for Hartnell College Chemistry 1

Funded by the Title V – STEM Grant #P031S090007 through Hartnell College

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Student Learning ObjectivesThis tutorial will help you to:1. Predict products of single and double-

replacement reactions2. Generate formula, total ionic and net

ionic equations using solubility and acid strength information

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Getting Started

This set of Power Point slides will lead you through a series of short lessons and quizzes on the topics covered by this Directed Learning Activity tutorial.

Move through the slideshow at your own pace. There are several hyperlinks you can click on to take you to additional information, take quizzes, get answers to quizzes, and to skip to other lessons.

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Table of Topics What You Should Know Classes of Chemical Reactions Single-replacement Reactions Double-replacement Reactions

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What You Should Know Write correct chemical formulas for

elements, ions and compounds Balance chemical formula equations Know the difference between strong and

weak acids and bases in solution

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Classes of Chemical ReactionsA Quick Overview of Synthesis, Decomposition, Single and Double-replacement Reactions

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The Four Major Classes of Chemical ReactionsThere are many different types of chemical reactions, but they can be broken down into these major categories: Synthesis (Combination) Reactions Decomposition Reactions Single-Replacement Reactions Double-Replacement ReactionsThe next few slides will explain the general characteristics of each category

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Synthesis (Combination)ReactionsSynthesis reactions can be written in symbols as:

Where A and B can be either elements or compounds and C is a new compound.

There are three kinds of synthesis reactions:1. Elements combine to form a compound2. An element and a compound combine3. Two compounds combine Next Slide

Decomposition Reactions

Decomposition reactions can be written in symbols as

Where AB is a compound, while A and B are elements or simpler compounds.

There are three kinds of decomposition reactions:1. Two (or more) elements are formed2. Elements and compounds form3. Two (or more) compounds form

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Single-replacement Reactions

Single-replacement reactions can be symbolized as

Where A and B are two elements and BC and AC are two compounds.

There are three basic kinds of single-replacement reactions:

1. A metal replaces another metal2. A metal replaces H to form H2 (g)

3. A nonmetal replaces another nonmetal

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Double-replacement ReactionsDouble-replacement reactions, also called “exchange” reactions, may be symbolized:

Where AB and CD are the original compounds and AD and BC are new compounds formed when the original compounds exchange ions or atoms.

There are three kinds of double-replacement reactions:1. Reactions in solution that form a precipitate (an

insoluble solid)2. Reactions that form a gas3. Reactions that form water (neutralization reactions)

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Details of Single-replacement Reactions

𝐴+𝐵𝐶→ 𝐴𝐶+𝐵Next Slide

Example: A Metal Replaces Another Metal in a Compound

In this case, solid Cu metal reaction with an aqueous solution of AgNO3. The Cu and Ag are exchanged and Cu(NO3)2 is formed in solution while solid Ag metal is formed.

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Example: A Metal Replaces H to Form H2 (g)

In this example, solid Mg metal reacts with HCl in solution. MgCl2 is the product formed in solution, while H2 gas is released. Note: in balancing this type of equation, remember that hydrogen is one of the diatomic molecular elements. Also, the most reactive metals (Group 1A and 2A) can undergo this type of reaction with water to form hydrogen gas. It is important to remember that this type of reaction often requires a strong acid, depending on the reactivity of the metal.

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Example: A Nonmetal Replaces Another Nonmetal

In this case a halogen (Group 7A) replaces another halogen in a compound. Note: as with hydrogen, halogens are diatomic molecular elements.

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Quiz Questions

? + ?

? + ?

? + ?

Answers to Quiz Questions

Answers to Quiz Questions

Next lessonReview this lesson

Double-replacement Reactions

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Example: Reactions in Solution that Form a Precipitate

A precipitate is a solid that forms in solution. In this example, the two reactants are both soluble in water. One of the products, NaNO3, is also soluble in water. The other product, AgCL, forms a solid precipitate. Note: there are cases when both products will form a precipitate.

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Example: Reactions that Form a Gas

In this reaction, two aqueous species eventually produce another aqueous species and a gas. Note: H2CO3, one of the products of the initial reaction, rapidly decomposes to create the gas CO2. Typical gases that can be produced in this kind of reaction include H2S. Note that this type of reaction may require a strong acid.

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Example: Reactions that Form Water

When an acid and a base are the reactants, this type of reaction is referred to as a neutralization reaction. The aqueous product is referred to as a “salt”. The salt has the cation from the base and the anion from the acid. Metal oxides can also react with acids to form water as a product.

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Quiz Questions

? + ?

? + ?

? + ?

Check answers

Answers to Quiz Questions

Next lessonReview lesson

Net Ionic EquationsGetting Rid of the Spectators

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Representing ReactionsWhen a reaction occurs in aqueous solution, we can write the formula equation, which uses the neutral formulas or symbols for the reactants and products. These are the kinds of equations you have already practiced writing. In certain instances, there are other ways of representing the reaction.The total ionic equation (TIE) separates all the neutral compounds into the ionic species they form in solution.The net ionic equation removes those ions from the equation that do not result in creating a new product. Those ions are called “spectator ions”, since they don’t actually participate in the formation of a new product.

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Example: Precipitation

Let’s use a reaction you have already seen.

This would be the formula equation.

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If we now break down everything that is soluble into ions and rewrite the equation, we obtain the total ionic equation:Ca2+ (aq) + 2 NO3- (aq) + 2 Na+ (aq) + CO3

2- (aq) → CaCO3 (s) + 2 Na+ (aq) + 2 NO3- (aq)

Inspecting this equation, we see that there are several ions that appear on both sides of the equation. These are the spectator ions. If we remove these, we obtain the net ionic equation:Ca2+ (aq) + 2 NO3- (aq) + 2 Na+ (aq) + CO3

2- (aq) → CaCO3 (s) + 2 Na+ (aq) + 2 NO3- (aq) or

Ca2+ (aq) + CO3 2- (aq) → CaCO3 (s)

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We can do similar procedures to the formula equations for the reactions that form gases and for neutralization of acids and bases.What if you are only given the starting materials and have to predict the products of the formula equation before you generate the net ionic equation?Then, you will have a use a table of solubilities like to the one on the next slide. There is probably one similar to it in your lecture text. You also need to know if the acids and bases are weak or strong. Remember that weak acids and bases do not completely dissociate and will be molecular species in solution. There is also an example table of strong acid and base on another slide.

Solubility Table

  Anions

Cations C2H3O2- AsO4

- Br - CO32- Cl - CrO4

2- OH - I - NO3- C2O4

2- O 2- PO43- SO4

2- S 2- SO32-

Al 3+ aq I aq - aq - I aq aq - I I aq d -

NH4+ aq aq aq aq aq aq aq aq aq aq - aq aq aq aq

Ba 2+ aq I aq I aq I sl. aq aq aq I sl. aq I I d I

Bi 3+ - sl. aq d I d - I I aq I I sl. aq d I -

Ca 2+ aq I aq I aq aq I aq aq I I I I d I

Co 2+ aq I aq I aq I I aq aq I I I aq I I

Cu 2+ aq I aq I aq I I - aq I I I aq I -

Fe 2+ aq I aq sl. aq aq - I aq aq I I I aq I sl. aq

Fe 3+ I I aq I aq I I - aq aq I I aq I -

Pb 2+ aq I I I I I I I aq I I I I I I

Mg 2+ aq d aq I aq aq I aq aq I I I aq d sl. aq

Hg2 2+ sl. aq I I I I sl. aq - I aq I I I I I -

Hg 2+ aq I I I aq sl. aq I I aq I I I d I -

Ni 2+ aq I aq I aq I I aq aq I I I aq I I

K + aq aq aq aq aq aq aq aq aq aq aq aq aq aq aq

Ag + sl. aq I I I I I - I aq I I I I I I

Na + aq aq aq aq aq aq aq aq aq aq aq aq aq aq aq

Sr 2+ aq - aq I aq I aq aq aq - - I I I -

Zn 2+ aq I aq I aq I I aq aq I I I aq I I

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Examples of Strong Acids & Bases Strong acids in aqueous solutions:

HClO4, H2SO4, HI, HBr, HCl, HNO3

Strong bases in aqueous solutions: LiOH, KOH, NaOH, Ca(OH)2

Remember that “strong” refers to species that dissociate (almost) completely to ions in water.

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Quiz Questions

Write the net ionic equations for these reactions:

K2SO4 (aq) + BaBr2 (aq) → ? + ?

Na2CO3 (aq) + 2 HCl (aq) → ? + ? + ?

Ca(OH)2 (aq) + 2 HCl (aq) → ? + H2O (l)

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Answers to QuestionsK2SO4 (aq) + BaBr2 (aq) → 2 KBr (aq) + BaSO4 (s)

Ba2+ (aq) + SO42- (aq) → BaSO4 (s)

Comment: look at solubility of the possible products to see that one of the products is solid. Delete the spectator ions to yield the net ionic equation.

Na2CO3 (aq) + 2 HCl (aq) →

2 NaCl (aq) + H2O (l) + CO2 (g)

2 H+ (aq) + CO32- (aq) → H2O (l) + CO2 (g)

Comment: Refer to gas generation example. Delete the spectator ions to generate the net ionic equation.Next slide

Ca(OH)2 (aq) + 2 HCl (aq) →

CaCl2 (aq) + 2 H2O (l)

2 H+ (aq) + 2 OH- (aq) → 2 H2O (l)Comment: This net ionic equation is common to all acid-base neutralization reactions

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© 2011 Hartnell College

Funded by the Title V – STEM Grant #P031S090007 through Hartnell College

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