Transcript Acids

Chapter 10 Acids (酸) and Bases （碱）
10.1 Acids donate protons, bases accept
them
• Sulfuric acid is the
number one
manufactured chemical,
85 billion pounds
(40,000,000 tons)
annually in US. Acid has
“sour” taste.
• Bases have “bitter” taste
and slippery feel. In US,
25 billion pounds
(10,000,000 tons) of
NaOH was manufactured.
Examples of acides
By definition, acids are chemicals that donate
hydrogen ions, and bases are chemicals that
accept them.
HCl + H2O
Cl- +H3O+ (hydronium ion)
H+ donor
H+ acceptor
(acid)
(base)
H 2O +
NH3
OH- +
NH4+
H+ donor H+ acceptor
H+ acceptorH+ donor
(acid)
(base)
(base)
(acid)
A salt is the product of an acidbase reaction (neutralization 中和)
Acid
Base
HCN
+
Hydrogen
Cyanide
Sodium
Hydroxide
HNO3 +
Nitric
acid
2HCl
2H2O
+
Hydrogen
Chloride
HF
+
Hydrogen
fluoride
NaOH
KOH
Salt
Water
NaCN +
Sodium
Cyanide
KNO3 + H2O
Potassium
Hydroxide
Potassium
nitrate
Calcium
Hydroxide
Calcium
chloride
Ca(OH)2
NaOH
Sodium
Hydroxide
H 2O
CaCl2 +
NaF
+ H 2O
Sodium
fluoride
Table10.1 acid-base reactions and the salts formed
10.2 Some acids and bases are stronger than
others
The stronger an acid, the more readily it donates
hydrogen ions.
The stronger a base, the more readily it accepts
hydrogen ions.
A nonelectrolyte
B strong electrolyte
C weak electrolyte
(a) The pure water in this circuit is unable to conduct electricity because it
contains practically no ions
(b) Because HCl is a strong acid, nearly all of its molecules break apart in
water, giving a high concentration of ions
(c) Acetic acid, C2H4O2, is a weak acid and in water only a small portion of
its molecules break up into ions
10.3 Solutions can be acidic, basic or neutral
In water, equal amount of
H3O+ and OH- (10-7M)
(neutral solution)
In acidic solution, more
H3O+ than OHIn basic solution, more
OH- than H3O+
Acidity 酸性 (and
basicity 碱性) can
be scaled by pH
value
pH = -log[H3O+]
10.4 Rainwater is acidic and ocean water is basic
The main sources
of acidic
rainwater are
CO2 and SO2.
The damage of
acidic rainwater
depends on the
local geology.
1. rain is acidified as it falls
through the air
2. acid enters lake from rain
3. hydronium ions are neutralized
by calcium carbonate released
from limestone
2H3O++CaCO3
3H2O+CO2+Ca2+
1.Rain is acidified as it falls
through the air
2. acid enters lake from rain
3. hydronium ions concentration
increases, with potential harm to
the ecosystem
Ocean can absorb CO2
Carbon
dioxide is
absorbed and
released
Carbon
dioxide
is absorbed
Fresh-water lake PH<7
Ocean PH=8.2
The concentration of CO2 in air has been
increased, which is related to global warming
Fig10.18 Researchers at
the Mauna Loa Weather
Observatory in Hawaii
have recorded increasing
concentrations of
atmospheric carbon
dioxide since they began
to collecting data in the
1950s.The chart left shows
how the concentration of
CO2 in the atmosphere has
changed in the last 40
years
10.5 Buffer solutions (缓冲溶液) resist
changes in pH
Effective buffer
solutions can
be prepared by
mixing a weak
acid with a salt
of the weak
acid.
Fig10.19 Hydrochloric acid added to a solution
containing acetic acid and sodium acetate is
neutralized by the sodium acetate to form
Additional acetic acid
Fig 10.20 Sodium hydroxide added to a
Solution containing acetic acid and sodium
Acetate is neutralized by the acetic acid
To form additional sodium acetate