Chapter 4 Class Essay

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Pages: 16

Chapter 4
Reactions in Aqueous Solutions

Summary of the Chapter

General properties of aqueous solutions

Precipitation reactions: soluble reactants could yield an insoluble product

Acid, bases and neutralization reactions: reactions in which H+ are transferred from one reactant to another

Concentrations in solutions: Molarity

Solution stoichiometry and chemical analysis: calculation of amounts and concentrations

General Properties of Solutions

• Solutions are defined as homogeneous mixture of two or more
pure substances.
• The solvent is the substance present in __________ greatest abundance.

• All ______ other substances are solutes. General Properties of Solutions
• The solvent is almost always a liquid. • The solute could be a solid (s), a liquid (l) or a gas (g).
If water is the solvent, then solutions are called aqueous solutions! • A saturated solution means that the maximum amount of solute has been added to the solvent and no more will go into solution.

Electrolytic Properties
• All aqueous solutions can be classified in terms of whether or not they conduct electricity.

Forms ions in solution

_________ electrolyte conducts electricity

Table salt or NaCl
Doesn’t Form ions in solution


Methanol in water

Doesn’t conduct electricity Electrolytic Properties

Ionic Compounds in Water
• When an ionic compound dissolves in water the ions dissocate are said to _________.
• Each ion is surrounded by several water molecules → aqueous ion (aq)
• These ions are said to be solvated. charge
• The transport of electric
by ions through the solution causes electric current to flow through the solution.

Ionic Compounds in Water



Na+(aq) + Cl

2 Na+(aq) + SO42-(aq)
+ CNK+(aq)
+ (aq)CN-(aq)

2+(aq) + 2 NO -(aq)

Molecular Compounds in Water
• When a molecular compound dissolves in water → molecules dispersed homogeneously in the
solution. nothing in the solution
• There is ________ to transport electric charge and the solution does not conduct electricity → nonelectrolytes

Important exceptions! ______ acids! __________________________
(g) forms H+ (aq) and Cl- (aq)

Which solution conducts electricity?
A. KCl(aq)

ionic compound

B. CH3OH(aq) (methanol) not ionic compound
C. (CH3)2CO (acetone)

not ionic compound


Strong and Weak Electrolytes aqueous soltuions conduct electricity well
• Compounds whose ___________ are called strong electrolytes.

entirely as ions
• Strong electrolytes exist in solution ____________!


Na+(aq) +


ionic compounds are strong electrolytes
• In general, soluble _____________
(we will see exception later).

• Other strong electrolytes include strong acids and soluble strong bases.


Na+(aq) +


once the ions are in the solution they have to conduct electricity

Strong and Weak Electrolytes increase the concentration of ____
H+ when dissolved
• Acids _______ on water. completely dissocates
• When for example HCl is added to water it _________, then is a strong electrolyte and strong acid!

HCl (aq)

H+ (aq) + Cl-(aq)

Strong and Weak Electrolytes increase OH• Bases _________ the concentration of _____ when dissolved on water.

• When for example NaOH is added to water it completely
then is a strong electrolyte and strong base!


Na+(aq) + OH-(aq)

Strong and Weak Electrolytes
• Compounds whose aqueous solutions conduct electricity poorly are called weak electrolytes. of ions and un-ionized
• These substances exist as a mixture _______________ molecules in solution.

CH3COOH (aq)

CH3COO- (aq) + H+(aq)

• Double arrow indicates that there is a balance between the forward and reverse reactions.
• This balance produces a state of chemical equilibrium.

Strong and Weak Electrolytes
• Weak acids: HF, H2SO3, HNO2, HClO, CH3COOH,