Chapter 7 – Reactions in Aqueous Solutions



Reactions in Aqueous Solutions, Predicting Products and Classifying Types of Chemical Reactions

I. Predicting Whether a Reaction Will Occur

Four Driving Forces

1)

2)

3)

4)

If a driving force occurs the reaction will take place.

II. Predicting States of Substances

A. Terms

1. Soluble solid – readily dissolves in water

2. Insoluble and slightly soluble solid – a solid where such a tiny amount dissolves in water that it is undetectable to the naked eye

3. Solubility is temperature dependent

3 Solubility Rules (back of snoopy sheet)

Mainly water soluble (aq)

1. All nitrates are soluble.

2. All acetates are soluble.

3. All chlorates are soluble.

4. All chlorides are soluble except AgCl, Hg2Cl2, and PbCl2

5. All bromides are soluble except AgBr, Hg2Br2, PbBr2, and HgBr2

6. All iodides are soluble except AgI, Hg2I2, PbI2, and HgI2

7. All sulfates are soluble except CaSO4, SrSO4, BaSO4, PbSO4, Hg2SO4, and Ag2SO4

Mainly water insoluble (s)

1. All sulfides are insoluble except those of 1A and 2A elements and (NH4)2S

2. All carbonates are insoluble except those of 1A and (NH4)2CO3

3. All phosphates are insoluble except those of 1A and (NH4)3PO4

4. All hydroxides are insoluble except those of 1A, Ba(OH)2, Sr(OH)2 and Ca(OH)2

Ex. Predict whether the following substances are soluble or insoluble.

C. When a soluble ionic salt dissolves in water the ions separate and a hydration shell is formed around each ion (Dissociation)

1. When a soluble ionic salt dissolves in water the ions separate.

Ex. Ba(NO3)2 in water –

Aluminum acetate

Aluminum carbonate

2. Draw a beaker of dissociated sodium chloride; a beaker of dissociated Aluminum nitrate; and a beaker of silver chloride.

D. Special rules

1. Acids are aqueous

2. Most metal oxides are solids

3. Most non-metal oxides are gases

III. Types of Reactions

A. Double Displacement:

Reactants are:

B. Single Displacement:

Reactants are:

C. Decomposition:

Reactants are:

D. Synthesis:

Reactants are:

E. Combustion:

Reactants are:

IV. Predicting Products

A. Double Displacement reactions: two compounds combine to produce two different compounds - Acid-Base and Precipitation Reactions.

* Use solubility rules.

General Equation:

Example:

B. Single Displacement reactions: an element and a compound combine to form a new element and compound.

* Use the activity series.

General Equation:

Example:

• Active metal elements can replace less active metals, active nonmetal elements can replace less active nonmetals.

• Use the Activity series (snoopy sheet) to determine whether or not the reaction will occur.

• Driving force is the transfer of electrons.

C. Decomposition reactions: a single compound is broken down into more than one product. There are six different types.

1. Decomposition of a binary compound into its elements.

* Usually requires heat or electricity.

General Equation:

Example:

2. Decomposition of a base into a metal-oxide and water.

General Equation:

Example:

3. Decomposition of a ternary acid into a nonmetal-oxide and water.

General Equation:

Example:

4. Decomposition of a metallic carbonate into a metal-oxide and carbon dioxide.

General Equation:

Example:

5. Decomposition of a metallic chlorate into a metal-chloride and oxygen gas.

General Equation:

Example:

6. Decomposition of a tertiary compound (other than the previous examples) into a metal-oxide and nonmetal-oxide

General Equation:

Example:

***Special Decompositions: Whenever H2CO3, H2SO3, or NH4OH is a product it will decompose immediately as follows:

▪ H2CO3 ( H2O + CO2

▪ H2SO3 ( H2O + SO2

▪ NH4OH ( H2O + NH3

D. Synthesis reactions: two substances combine to form one product. There are four different types.

1. Two elements combine to form a binary compound.

General Equation:

Example:

2. Combining a metal-oxide and water to produce a base.

General Equation:

Example:

3. Combining a nonmetal–oxide and water to produce a tertiary acid.

General Equation:

Example:

4. Combining a metal-oxide and a nonmetal-oxide to produce a tertiary salt.

General Equation:

Example:

E. Combustion reactions: Certain organic compounds (Hydrocarbons – compound containing Carbon and Hydrogen or Carbon, Hydrogen and Oxygen) burn to produce specific products. There are two types.

1. Complete combustion – combining a hydrocarbon with excess oxygen to produce carbon dioxide and water.

**if the equation does not indicate limited oxygen assume complete combustion

General Equation:

Example:

2. Incomplete combustion - combining a hydrocarbon with limited oxygen to produce carbon monoxide and water.

General Equation:

Example:

F. Oxidation-Reduction reactions: (redox)

• Driving Force = Transfer of electrons

• Always in single displacement reactions

• Sometimes in Synthesis and Decomposition

• Never in Double Displacement

Example:

2 NaCl (aq) ( 2 Na (s) + Cl2 (g)

2 Na (s) + Cl2 (g) ( 2 NaCl (aq)

Zn(NO3)2(aq) + 2 Na(s) ( 2NaNO3(aq) + Zn(s)

-----------------------

AB ( A + B

A + B ( AB

CxHx + O2 ( CO2 + H2O

Reactant is: 1 compound

Reactants are: 2 elements or 2 oxides

Reactants are: hydrocarbon and oxygen

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