Prentice Hall © 2003 Chapter 4

Chapter 4Aqueous Reactions and Solution

Stoichiometry

Prentice Hall © 2003 Chapter 4

Electrolytic Properties• Aqueous solutions have the potential to conduct electricity

(ions needed)• There are three types of solutions:

• Strong electrolytes• Weak electrolytes• Nonelectrolytes

4.1 General Properties of 4.1 General Properties of Aqueous SolutionsAqueous Solutions

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Ionic Compounds in Water• Ions dissociate (break apart) in water

• In solution, each ion is surrounded by water molecules

• Transport of ions through solution causes flow of current

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Molecular Compounds in Water• Molecular compounds in water: no ions are formed

• If there are no ions in solution, there is nothing to transport electric charge

Prentice Hall © 2003 Chapter 4

Electrolytic Properties

Prentice Hall © 2003 Chapter 4

Strong and Weak Electrolytes

• Strong electrolytes: completely dissociate in solution• Acids ionize

• Soluble Salts

• Strong Acids (HCl, HBr, HI, HNO3, HClO4, HClO3, H2SO4) HCl(aq) H+(aq) + Cl-

(aq)

KNOW THE 7 STRONG ACIDS!

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• Weak electrolytes: produce a small concentration of ions when they dissolve (weak acids)

– These ions exist in equilibrium with the un-ionized substance

– For example:HC2H3O2(aq) H+(aq) + C2H3O2

-(aq)

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• Sample Problems # 5 & 9

Prentice Hall © 2003 Chapter 4

• When two aqueous solutions are mixed and a solid is formed, the solid is called a precipitate

4.2 Precipitation Reactions4.2 Precipitation Reactions

Text, P. 118

You must know your Solubility Rules: there

will be a quiz!

Prentice Hall © 2003 Chapter 4

• Sample Problem # 11

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Exchange (Metathesis) Reactions• Metathesis reactions involve swapping ions in solution:

• (anions/cations switch partners)

AX + BY AY + BX

• Metathesis reactions will lead to a change in solution if one of three things occurs:– an insoluble solid is formed (precipitate)– weak or nonelectrolytes are formed– an insoluble gas is formed

Signs of a chemical reaction!

Prentice Hall © 2003 Chapter 4

• These are not to be confused with replacement reactions:

Zn(s) +2HCl(aq) ZnCl2(aq) + H2(g)

• These have the general form A + BX AX + B

and are usually Redox (more on this at a later time)

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• Sample Problems # 13, 17, 19