Download Acids and bases in industrial processes

Lesson 12: Acids and Bases In Our Bodies and In Industry
Introduction
As you have seen in the previous lesson, acids and bases are present around us and in us.
We flavour foods with acids and use them to preserve food. We have acids and bases in our
bodies to help with digesting our food. We use them for baking and as medicines. Acids are
important in many other chemical processes in our bodies.
Acids are very important in industrial processes. Acids and bases are used in a wide variety
of industrial processes.
Outcomes
After completing this lesson, you will be able to:



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Describe the roles of acids and bases in digestion in the human body
Describe the role of sulfuric acid as catalyst in industry
Explain why citrus fruits and pickles taste sour
Describe the roles of acids and bases in biological systems other than humans
Key Words
citric acid
Catalyst
Sulphuric acid
Hydrochloric acid
Nitric acid
Sodium bicarbonate
Corrosive
hydrofluoric acid
Ammonium nitrate Carcinogenic
Acids and bases in human biological systems

stomach acid (hydrochloric acid) HCl
You may have noticed in lesson 11 that stomach fluids have a pH of 1.7 - a strong
acid. This hydrochloric acid, along with some enzymes, is responsible for partially
breaking down proteins in the food you eat.
How does your stomach keep from digesting itself? (From How Stuff
Works.com)
Your stomach is a "crescent-shaped hollow organ" about the size of a large melon.
The average adult stomach holds about three quarts (three litres) of fluid. Your
stomach is made up of a variety of layers, including:
o
The serosa - the outer layer that acts as a covering for the other layers.
o
Two muscle layers - the middle layers that propel food from the stomach into
the small intestine.
o
The mucosa - the inner layer made up of specialized cells, including parietal
cells, g-cells and epithelial cells.
o
Parietal cells, which produce hydrochloric acid, a strong acid that helps to
break down food. The acid in your stomach is so concentrated that if you
were to place a drop on a piece of wood, it would eat right through it.
o
The g-cells produce gastrin, a hormone that facilitates the production of
hydrochloric acid by the parietal cells.
The stomach is protected by the epithelial cells, which produce and secrete a
bicarbonate-rich solution that coats the mucosa. Bicarbonate is alkaline, a base, and
neutralizes the acid secreted by the parietal cells, producing water in the process.
This continuous supply of bicarbonate is the main way that your stomach protects
itself from autodigestion (the stomach digesting itself) and the overall acidic
environment.
In some individuals, due to impairments in blood supply to the stomach, or to
overproduction of acid, this defence system does not work as well as it should.
These people can get gastric ulcers. There are also specific bacteria, called
Helicobacter pylori that may cause impairment of the stomach's defences and can
also be responsible for ulcers.

pancreatic fluid (includes sodium bicarbonate) NaHCO3
The pancreas contains sodium bicarbonate (NaHCO3). This neutralizes the acidity of
the fluid arriving from the stomach raising its pH to about 8. Since the stomach is
the only organ that can manage strong acids, this raising of pH in the fluid leaving
the stomach is important. A strong acidic solution would damage the small intestine
into which flow the contents of the stomach.
Acids and bases in other biological systems
citrus fruit (citric acid)
Citric acid is an organic acid found in citrus fruits such as oranges (pH 3.5), grapefruit (pH
3.1), and lemons (pH 2.6). Citric acid gives the juice of citrus fruits their characteristic
“tangy” taste.
bee and wasp stings (formic acid)
The venom in stings from insects such as ants, bees and wasps can release formic acid along
with other toxins (poisons) into our bodies. Formic acid can hinder our ability to breathe.
Occasionally the response is severe enough to require medical attention.
Acids and bases in industrial processes

Explosives (nitric acid) HNO3
Nitric acid is very important for certain types of reactions and uses especially in the
fertilizer and explosives industries. The principle use for nitric acid is the production
of fertilizers, explosives, flares, and rocket propellants. In making explosives, nitric
acid reacts with toluene in the presence of sulfuric acid to form trinitrotoluene
(TNT).
An indirect use of nitric acid can be observed in plants. Plants need nitrogen to make
amino acids, peptides, and proteins. However, they cannot use nitrogen gas (N2)
from the air. The plants therefore, get their nitrogen from the Nitrogen Cycle. Nitric
acid comes into play during the nitrogen cycle. "Large quantities of nitric acid are
produced during thunderstorms and fall to the earth in rain. The rain falls as a very
weak solution of nitric acid. The production of nitric acid during thunderstorms
allows nitrogen in the air to become part of the soil," therefore allowing the plants to
fulfill their nitrogen needs ("Nitric Acid" World Book Encyclopedia, The).
Other uses include manufacturing nylon, preparing materials for use on stone in
lithography, and to test whether certain jewelry is genuine gold or platinum. Nitric
acid contains a powerful oxidizing agent that, when mixed with hydrochloric acid,
dissolves many metals except gold or platinum.

Fertilizers (ammonia) NH3
Prior to World War II, animal and other manures were commonly used on farms as
fertilizers. World War II brought a need to produce nitrogen for explosives. Eleven
factories were constructed to produce nitrogen. After WWII they were used to
produce fertilizer.
Plants need light, warmth, carbon dioxide and warmth for growth to take place.
Plants also require several elements for growth; these elements include nitrogen,
potassium and phosphorous. To help the soil supply all the nutrient requirements for
plant growth, farmers often provide nitrogen compounds in the form of fertilizers.
The most commonly lacking element is nitrogen. Nitrogen is provided through the
use of ammonia(NH3). Ammonia reacts with nitric acid to form an ammonium salt
that contains nitrogen:
HNO3(aq) + NH3(g)
Nitric acid + ammonia
NH4NO3(aq)
ammonium nitrate
Ammonium nitrate contains nitrogen that is easily absorbed by the plants.

Glass Etching (hydrofluoric acid) HF
Hydrofluoric acid is the chemical used for glass etching, which is the process of
the acid corroding the surface of the glass to leave a pattern on the glass.
Hydrofluoric acid is extremely dangerous and can leave severe burns on exposed
skin.

Speeding up industrial chemical reactions (sulfuric acid) H2SO4
Sulfuric acid is one of the most important industrial chemicals. More of it is made
each year than of any other manufactured chemical; more than 40 million tons of it
was produced in the United States in 1990. It has widely varied uses and plays some
part in the production of nearly all manufactured goods. Sulfuric acid is used as a
catalyst, a material that speeds up a chemical reaction.
o The major use of sulfuric acid is in the production of fertilizers, e.g.,
superphosphate of lime and ammonium sulfate.
o
It is widely used in the manufacture of chemicals, e.g., in making
hydrochloric acid, nitric acid, sulfate salts, synthetic detergents, dyes and
pigments, explosives, and drugs.
o
It is used in petroleum refining to wash impurities out of gasoline and other
refinery products.
o
Sulfuric acid is used in processing metals, e.g., in pickling (cleaning) iron
and steel before plating them with tin or zinc.
o
Rayon is made with sulfuric acid.
o
Sulfuric acid serves as the electrolyte in the lead-acid storage battery
commonly used in motor vehicles.
Sulfuric acid is a clear, colourless to dark brown, odourless, dense, oily liquid. It will
not burn but it can decompose at high temperatures forming toxic gases, such as
sulfur oxides. Contact of sulfuric acid with combustible materials may cause fire. It
is considered to be highly reactive. Contact with many organic and inorganic
chemicals may cause fire or explosion and contact with metals liberates flammable
hydrogen gas. It also reacts violently with water.
Sulfuric acid is VERY TOXIC. It may be fatal if inhaled or swallowed and it is
CORROSIVE to the eyes, skin and respiratory tract. It may cause blindness and
permanent scarring. It also causes lung injury and these effects may be delayed.
Strong inorganic acid mists containing sulfuric acid are CARCINOGENIC; that is,
they can cause cancer if you are exposed to them.
Acids and bases in industrial processes

Explosives (nitric acid) HNO3
Nitric acid is very important for certain types of reactions and uses especially in the
fertilizer and explosives industries. The principle use for nitric acid is the production
of fertilizers, explosives, flares, and rocket propellants. In making explosives, nitric
acid reacts with toluene in the presence of sulfuric acid to form trinitrotoluene
(TNT).
An indirect use of nitric acid can be observed in plants. Plants need nitrogen to make
amino acids, peptides, and proteins. However, they cannot use nitrogen gas (N2)
from the air. The plants therefore, get their nitrogen from the Nitrogen Cycle. Nitric
acid comes into play during the nitrogen cycle. "Large quantities of nitric acid are
produced during thunderstorms and fall to the earth in rain. The rain falls as a very
weak solution of nitric acid. The production of nitric acid during thunderstorms
allows nitrogen in the air to become part of the soil," therefore allowing the plants to
fulfill their nitrogen needs ("Nitric Acid" World Book Encyclopedia, The).
Other uses include manufacturing nylon, preparing materials for use on stone in
lithography, and to test whether certain jewelry is genuine gold or platinum. Nitric
acid contains a powerful oxidizing agent that, when mixed with hydrochloric acid,
dissolves many metals except gold or platinum.

Fertilizers (ammonia) NH3
Prior to World War II, animal and other manures were commonly used on farms as
fertilizers. World War II brought a need to produce nitrogen for explosives. Eleven
factories were constructed to produce nitrogen. After WWII they were used to
produce fertilizer.
Plants need light, warmth, carbon dioxide and warmth for growth to take place.
Plants also require several elements for growth; these elements include nitrogen,
potassium and phosphorous. To help the soil supply all the nutrient requirements for
plant growth, farmers often provide nitrogen compounds in the form of fertilizers.
The most commonly lacking element is nitrogen. Nitrogen is provided through the
use of ammonia(NH3). Ammonia reacts with nitric acid to form an ammonium salt
that contains nitrogen:
HNO3(aq) + NH3(g)
Nitric acid + ammonia
NH4NO3(aq)
ammonium nitrate
Ammonium nitrate contains nitrogen that is easily absorbed by the plants.

Glass Etching (hydrofluoric acid) HF
Hydrofluoric acid is the chemical used for glass etching, which is the process of
the acid corroding the surface of the glass to leave a pattern on the glass.
Hydrofluoric acid is extremely dangerous and can leave severe burns on exposed
skin.

Speeding up industrial chemical reactions (sulfuric acid) H2SO4
Sulfuric acid is one of the most important industrial chemicals. More of it is made
each year than of any other manufactured chemical; more than 40 million tons of it
was produced in the United States in 1990. It has widely varied uses and plays some
part in the production of nearly all manufactured goods. Sulfuric acid is used as a
catalyst, a material that speeds up a chemical reaction.
o The major use of sulfuric acid is in the production of fertilizers, e.g.,
superphosphate of lime and ammonium sulfate.
o
It is widely used in the manufacture of chemicals, e.g., in making
hydrochloric acid, nitric acid, sulfate salts, synthetic detergents, dyes and
pigments, explosives, and drugs.
o
It is used in petroleum refining to wash impurities out of gasoline and other
refinery products.
o
Sulfuric acid is used in processing metals, e.g., in pickling (cleaning) iron
and steel before plating them with tin or zinc.
o
Rayon is made with sulfuric acid.
o
Sulfuric acid serves as the electrolyte in the lead-acid storage battery
commonly used in motor vehicles.
Sulfuric acid is a clear, colourless to dark brown, odourless, dense, oily liquid. It will
not burn but it can decompose at high temperatures forming toxic gases, such as
sulfur oxides. Contact of sulfuric acid with combustible materials may cause fire. It
is considered to be highly reactive. Contact with many organic and inorganic
chemicals may cause fire or explosion and contact with metals liberates flammable
hydrogen gas. It also reacts violently with water.
Sulfuric acid is VERY TOXIC. It may be fatal if inhaled or swallowed and it is
CORROSIVE to the eyes, skin and respiratory tract. It may cause blindness and
permanent scarring. It also causes lung injury and these effects may be delayed.
Strong inorganic acid mists containing sulfuric acid are CARCINOGENIC; that is,
they can cause cancer if you are exposed to them.
Summary
Acids and bases perform important functions in the human bodies. Your body has systems
to control the amount of acid or base so that there is just the correct amount to do the job.
Your body makes use of the fact that acids and bases neutralize each others properties to
prevent them from harming you.
Acids and bases used in industry are more powerful than the acids and bases in your body.
In industry, the acids and bases are also very concentrated so that they can do their jobs
quickly. This tends to make these materials very dangerous to handle as they are highly
corrosive.
Exercise
Questions
1. The stomach produces its own hydrochloric acid to aid in the digestion of food and
yet it doesn’t damage itself. Three types of cells (parietal cells, g-cells and epithelial
cells) help in the process of hydrochloric acid production and stomach protection.
Describe how these cells function.
2. The stomach produces highly acidic hydrochloric acid but the small intestine cannot
manage such low pH material. How does your body raise the pH of the fluid
entering the small intestine?
3. Which of the three citrus fruits - oranges, grapefruits and lemons - would taste the
most sour? Give your reason for your choice.
4. Name three ways that sulphuric acid is used as an aid in industrial production.
5. Name the common fertilizer chemical that is used by farmers to provide nitrogen for
plants.
6. What common explosive is produced from nitric acid?
7. What is a catalyst? Which acid is widely used as catalyst in industry?
8. What is glass etching?
9. Where is sulphuric acid used in a car?