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)