Applications of
Acids, Bases,
and
Neutralization
Reactions
Agricultural Impacts and Uses
The successful growth of plants in agriculture depends
on many conditions that must be met for optimal
plant growth. Soil pH is one of these conditions.
Different plants grow best in different conditions of soil
acidity.
Changes in soil pH can affect the following aspects of
plants growth:
Plants can only use dissolved nutrients in the soil. The
pH of the soil can affect the composition of
dissolved nutrients in the soil
Microorganisms usually require environments with a
certain pH to thrive. Some microorganisms in the soil
can be advantageous to plant growth and soil pH
could affect the composition of soil microflora
The pH of the soil can affect the colour of flowers
and therefore can be useful for producing a desired
product
Commercial Impacts and Uses
Pharmaceutical production – changing pH of
solutions can cause products to precipitate out of
solution. If the precipitate is a desired product, pH
can be changed to encourage precipitation.
Household pharmaceuticals –
bases such as antacids can be
used to treat heart burn by
helping to neutralize
stomach acids
Commercial Impacts and Uses
Household cleaning – bases are often found in
cleaning products and feel slipper to the touch
Pool maintenance – pools must be maintained at a
near neutral pH to be safe for use and to maintain
the effectiveness of the chlorine.
Environmental Impacts and Uses
Acid precipitation
Rain usually has a pH of 5.6. A pH of lower than that
is considered acid rain. Acid rain is caused by
reactions in the atmosphere involving water and
various non-metal oxides. These gases are released
into the atmosphere by transportation, various
industries, and natural sources.
The formation of acid rain is a chain of reactions
involving gases released from industry. The two main
processes are shown below, involving sulfur dioxide
(SO2) and nitrogen oxides (NOx).
Reactions with sulfur dioxide:
1. The combustion of fossil fuels containing sulfur
results in the production of sulfur dioxide from sulfur
and oxygen
S(s) + O2(g) SO2(g)
2. The sulfur dioxide gas then further reacts with
oxygen to produce sulfur trioxide.
2 SO2(g) + O2(g) 2 SO3(g)
3. This sulfur trioxide gas then reacts with water in the
atmosphere to form sulfuric acid.
SO3(g) + H2O(l) H2SO4(aq)
Reactions with nitrogen oxides:
1. Combustion in engines cause nitrogen gas and
oxygen gas to react and form nitrogen monoxide
gas.
N2(g) + O2(g) 2 NO(g)
2. The nitrogen monoxide gas then further reacts with
oxygen gas to produce nitrogen dioxide gas.
2 NO(g) + O2(g) 2 NO2(g)
3. This nitrogen dioxide gas then reacts with water in
the atmosphere to form nitric acid.
3 NO2(g) + H2O(l) 2 HNO3(aq) + NO(g)
Effects of Acid RainThe effects of acid rain include the following:
impacts on aquatic ecosystems as most organisms
have a narrow range of pH that is considered
optimal
changes to soil pH and soil composition
economic impacts resulting from loss of product in
industry (fishing,
agriculture, etc.)
or city maintenance
and repair of
structures
Prevention of Acid Rain and
Remediation
Reduction of NOx and SO2 emissions
Use of catalytic converters in vehicles to reduce
NOx emission
metal catalysts such as platinum help to reduce the
emission of harmful gases
Prevention of Acid Rain and
Remediation
Use of scrubbers in smokestacks to reduce SO3
the decomposition products of calcium carbonate are
used to decrease harmful emissions
Prevention of Acid Rain and
Remediation
Decrease acidity of lakes
calcium hydroxide (limewater) is a compound that
can be used to neutralize the acidity of lakes.
However, liming can have negative impacts such as
increasing the calcium content of the lake.
Acid Leaching Heavy metals can be released into the environment
through many pathways.
Acids can react with metals in soil to produce
soluble compounds. This process is known as acid
leaching. In uncontrolled environments, this can be
very damaging as it releases metals and other
substances into the surrounding environment.
However, acid leaching can also be used to clean
up soils in a controlled
manner where the soluble
compounds (including the
unwanted metals) can be
removed from the soil.
Chemical Spills
Large amounts of industrial chemicals are often
transported over long distances. If an accident
occurs, knowledge of neutralization reactions can
be used to clean up spills of large amounts of acid
or base.
For example, after the
derailing of a train in
northern Ontario, a large
amount of sulfuric acid
was spilled and released
into the nearby river.
Chemical Spills
To neutralize the acid, they added calcium oxide (lime) to the river to cause the following chain of reactions which neutralizes the acid:
1. The added calcium oxide reacts with the water in the river to form the base calcium hydroxide.
CaO(s) + H2O(l) Ca(OH)2(aq)
2. This calcium hydroxide then reacts with the sulfuric acid in the river in a neutralization reaction.
Ca(OH)2(aq) + H2SO4(aq) 2 H2O(l) + CaSO4(aq)
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