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Acids and Bases Introduction
Chem 12
Chapter 14 Pg 544-559
Properties of Acids
• Turn blue litmus paper red
• Neutralize the properties of bases
• React with certain metals to produce hydrogen
gas
• React with carbonate compounds to produce
carbon dioxide gas
• Have a sour taste
• Are electrolytes
• Have a pH less than 7
Properties of Bases
• Turn red litmus paper blue
• Turn the indicator phenolphthalein from
colorless to red
• Neutralize the properties of acids
• Have a bitter taste
• Are electrolytes
• Are slippery to the touch
• Have a pH greater than 7
Common Acids
Sulfuric Acid
H2SO4
Battery acid
Nitric Acid
HNO3
Used to make fertilizers
and explosives
Phosphoric Acid
H3PO4
Food flavoring
Hydrochloric Acid
HCl
Stomach acid
Acetic Acid
Carbonic Acid
CH3COOH
H2CO3
Vinegar
Carbonated water
Common Bases
Name
Formula
Common Name
Sodium hydroxide
NaOH
lye or caustic soda
Potassium hydroxide
KOH
lye or caustic potash
Magnesium hydroxide
Mg(OH)2
milk of magnesia
Calcium hydroxide
Ca(OH) 2
slaked lime
Ammonia water
NH3. H2O
household ammonia
Definition of Acid
• An operational definition is a definition based on
observed experimental properties.
• An operational definition of an acid is that it is a
substance that turns blue litmus paper red and
has a pH less than 7.
• An operational
definition of a base
is that it is a
substance that turns
red litmus paper
blue and has a pH
greater than 7.
• A conceptual definition attempts to explain
why a substance behaves the way it does.
• Arrhenius theory (only applies to solutions
made with water) and Bronsted-Lowery
acid base definitions are conceptual
Arrhenius Acid-Base Theory
• An acid is a substance that produces
hydrogen ions, H+ (aq), in water.
Hydrogen ions always combine with at
least one water molecule to produce
hydronium ions, H3O+
HCl(g) + H2O(l) < -- > H3O+ (aq) + Cl-(aq)
Arrhenius acid (hydrochloric acid)
Arrhenius Base
• A base is a substance that produces
hydroxide ions, OH- (aq), in water.
NaOH(s) + H2O(l) → Na+ (aq) + OH-(aq)
Arrhenius base (sodium hydroxide)
• According to the Arrhenius acid-base
theory, the hydronium ion explains the
chemical properties of an acid, and the
hydroxide ion explains the chemical
properties of a base.
• acid-base neutralization the hydronium ion
from the acid reacts with the hydroxide ion
from the base to produce water.
H3O+(aq) + OH-(aq) → 2H2O(l)
Brønsted-Lowry acid-base theory
• An acid is proton (H+ ion) donor, and a base is a
proton (H+ ion) acceptor.
• This is a better definition because it is not limited
to solutions where water is the solvent.
Acid (proton donor)
Base (proton
acceptor)
Monoprotic Acids
• Bronsted-Lowry acids can be
monoprotic-capable of losing one proton,
such as:
HCl(aq) + H2O(l)  H3O+(aq) + Cl-(aq)
HNO3(aq) + H2O(l)  H3O+(aq) + NO3-(aq)
• Bronsted-Lowry acids can also be
polyprotic-capable of losing
(donating) more than one proton.
• Polyprotic acids lose their protons in
separate steps or reactions.
Diprotic Acids
• Diprotic acids are capable of losing two protons.
H2SO4(aq) + H2O(l)  HSO4-(aq) + H3O+(aq)
HSO4-(aq) + H2O(l)  SO42-(aq) + H3O+(aq)
Polybasic Bases
• Bronsted-Lowry bases can be
monobasic-capable of supplying one
hydroxide ion such as
NaOH(s) + H2O(l)  Na+(aq) + OH-(aq)
• Polybasic bases can be capable of
supplying more than one hydroxide ion.
• Dibasic are capable of supplying two
hydroxide ions.
Mg(OH)2(s) + H2O(l)  Mg2+(aq) + 2OH-(aq)
Conjugate Acid-Base Pairs
• A pair of substances that only differ by one
proton.
• Conjugate = “linked together”
H+ donor
NH4+ + CO3-2 < -- > NH3 + HCO3Acid
base
conjugate conjugate
base
acid
Conjugate acid and base, HA/A-, differ
by one proton.
The conjugate acid of a base is the
base plus the attached proton and the
conjugate base of an acid
is the acid minus the proton.
Conjugate Acid-Base Pairs
Kelter, Carr, Scott, Chemistry A World of Choices 1999, page 280
Amphoteric
•
Substances that can act like an acid in
one reaction, and like a base in another
type of reaction.
• Example: baking soda’s anion HCO31. HCO3- + OH- < -- > CO3-2 + H2O
(donates a H+, so acts like an acid)
2. HCO3- + H3O+ < -- > H2CO3 + H2O
(accepts a H+, so acts like a base)
Practice:
Finish these questions for homework
Page 557 #1-9