Prentice Hall © 2003Chapter 4 Chapter 4 Aqueous Reactions and Solution Stoichiometry

Prentice Hall © 2003Chapter 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 Aqueous Solutions

Prentice Hall © 2003Chapter 4 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

Prentice Hall © 2003Chapter 4 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 © 2003Chapter 4 Electrolytic Properties

Prentice Hall © 2003Chapter 4 Strong and Weak Electrolytes Strong electrolytes: completely dissociate in solution Acids ionize Soluble Salts Strong Acids (HCl, HBr, HI, HNO 3, HClO 4, HClO 3, H 2 SO 4 ) HCl (aq)  H + (aq) + Cl - (aq) KNOW THE 7 STRONG ACIDS!

Prentice Hall © 2003Chapter 4 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:

Prentice Hall © 2003Chapter 4 Sample Problems # 5 & 9

Prentice Hall © 2003Chapter 4 When two aqueous solutions are mixed and a solid is formed, the solid is called a precipitate 4.2 Precipitation Reactions

Text, P. 118 You must know your Solubility Rules: there will be a quiz!

Prentice Hall © 2003Chapter 4 Sample Problem # 11

Prentice Hall © 2003Chapter 4 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 © 2003Chapter 4 These are not to be confused with replacement reactions: Zn (s) +2HCl (aq)  ZnCl 2(aq) + H 2(g) These have the general form A + BX  AX + B and are usually Redox (more on this at a later time)

Prentice Hall © 2003Chapter 4 Sample Problems # 13, 17, 19