chapter 4 aqueous reactions and solution...
TRANSCRIPT
Aqueous
Reactions1
Aqueous
Reactions
Chapter 4
Aqueous Reactions and
Solution Stoichiometry
Aqueous
Reactions
4.1 General Properties of Aqueous
Solutions
• Solutions are homogeneous
mixtures of two or more pure
substances.
• The substance present in the
greatest quantity is the solvent.
• The other substances present are
called solutes. They are said to be
dissolved in the solvent.
• Solute + solvent = solution
• Ex: salt dissolved in water3
Aqueous
Reactions
Electrolytes
• An electrolyte is a substance
that dissociates into ions
when dissolved in water.
• Electrolyte solutions conduct
electricity.
• A nonelectrolyte (sugar, for
example) may dissolve in
water, but it does not
dissociate into ions when it
does so.
• Nonelectrolyte solutions do
not conduct electricity.
4
Aqueous
Reactions
Ionic Compounds in Water
• When an ionic substance dissolves in
water it undergoes dissociation.
• The water molecules pull individual ions
from the crystal and surrounds them in
a process called solvation.
• Water is a polar
molecule, so the
negatively charged side
is attracted to cations
(+) and the positively
charged side is
attracted to anions (-).
5
Aqueous
Reactions
Electrolytes and Nonelectrolytes
Soluble ionic
compounds tend to
be electrolytes.
6
Aqueous
Reactions
Electrolytes and Nonelectrolytes
Molecular compounds
tend to be
nonelectrolytes, except
for acids and bases.
7
Aqueous
Reactions
Electrolytes
• A strong electrolyte
dissociates completely
when dissolved in water.
• Essentially all soluble
ionic compounds and a
few molecular compounds
are strong electrolytes.
• A weak electrolyte only
dissociates partially when
dissolved in water.
8
Aqueous
Reactions
Strong Electrolytes Are…
• Strong acids
9
Aqueous
Reactions
Strong Electrolytes Are…
• Strong acids
• Strong bases
10
Aqueous
Reactions
Strong Electrolytes Are…
• Strong acids
• Strong bases
• Soluble ionic salts
11
Aqueous
Reactions
4.2 Precipitation Reactions
When one mixes ions
that form compounds that
are insoluble (as could
be predicted by the
solubility guidelines), a
precipitate is formed.
12
Aqueous
Reactions
Metathesis (Exchange) Reactions
• Metathesis comes from a Greek word that
means “to transpose”
• It appears the ions in the reactant
compounds exchange, or transpose, ions
AgNO3 (aq) + KCl (aq) AgCl (s) + KNO3 (aq)
13
Aqueous
Reactions
Solution Chemistry
• It is helpful to pay attention to exactly what
species are present in a reaction mixture (i.e.,
solid, liquid, gas, aqueous solution).
• If we are to understand reactivity, we must be
aware of just what is changing during the
course of a reaction.
14