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
nonelectrolyte
___________
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
Examples:
NaCl(s)
Na2SO4
(s)
Na
2SO4(s)
KCN(s)
Fe(NO3)2(s)
Cl--(aq)
(aq)
Na+(aq) + Cl
2 Na+(aq) + SO42-(aq)
K+
+ CNK+(aq)
(aq)
+ (aq)CN-(aq)
Fe2+
2+(aq) + 2 NO -(aq)
Fe
3
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! __________________________
HCl
(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
KCl(aq)
Strong and Weak Electrolytes aqueous soltuions conduct electricity well
• Compounds whose ___________ are called strong electrolytes.
entirely as ions
• Strong electrolytes exist in solution ____________!
NaCl(s)
Na+(aq) +
Cl-(aq)
ionic compounds are strong electrolytes
• In general, soluble _____________
(we will see exception later).
• Other strong electrolytes include strong acids and soluble strong bases.
NaOH(s)
Na+(aq) +
OH-(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.
dissocates
• When for example NaOH is added to water it completely
__________,
then is a strong electrolyte and strong base!
NaOH(aq)
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,