Transcript Acid Deposition

Acid Deposition
pH Scale
 7 is neutral
 As numbers decrease, acidity increases
 As numbers increase, alkalinity
increases
pH Scale
 Q - How much more acidic is a pH of 3
than a pH of 7?
 A – 10,000 times
 pH is a logarithmic scale
Rain
 From a natural and unpolluted
atmosphere has a pH of close to 6.0
 Results form reaction of water vapor
and CO2 in the atmosphere forming a
weak carbonic acid (H2CO3):
 CO2(g)
+ H2O(l)
H2CO3(aq)
 Since carbonic acid is a weak acid it
partially dissociates:
 CO2(g)
+ H2O(l)
+
-
H (aq) + HCO3 (aq)
Acid Rain
 Has a pH below 5.6
 Reaction of water vapor with sulfur
dioxide (SOx) and nitrogen oxides (NOx)
Acid Rain form Sulfur
compounds (SOx)
 Sulfur dioxide reacts with water to form
sulfurous acid (H2SO3):
 SO2(g)
+ H2O(l)
H2SO3(aq)
 Sulfur dioxide (SO2) can be oxidized
gradually to sulfur trioxide (SO3):
 2SO2(g)
+ O2(g)
2SO3(g)
 Sulfur trioxide (SO3) reacts with water
to form sulfuric acid (H2SO4):
 SO3(g)
+ H2O(l)
H2SO4(aq)
Acid Rain from Nitrogen
compounds (NOx)
 Oxides of nitrogen, particularly nitrogen
dioxide (NO2) react with water to form
nitrous acid (HNO2) and nitric acid
(HNO3):
 2NO2(g)
+ H2O(l)
HNO2(aq) + HNO3(aq)
Effects of Acid Rain
 Damages buildings and marble statues
by reacting with calcium carbonate to
from soluble calcium hydrogen
carbonate (calcium bicarbonate,
Ca(HCO3)2):
 CaCO3
+ acid rain
Ca(HCO3)2
Effects of Acid Rain
Effects of Acid Rain
 Leaches aluminum and calcium form
the soil into the ground water, lakes and
rivers; poisoning fish and plant roots
 Aluminum
reacts negatively with the gills of
the fish
irritating them
 causing a build up of mucous
 resulting in suffocation

Effects of Acid Rain
 Disrupts the process of photosynthesis
 Damages
plant life
Slows the production of chlorophyll
 Sulfuric acid kills plants

 “Crown
dieback”
Leaves at the top (crown) of trees die
 Leaving a sparse thin crown that progressively
increases and moves its way down the tree

Crown Dieback
Assignment
 3.5.1 and 3.5.2 – Chemistry of acid
Precipitation and Possible Effects