Transcript Lesson 4 Ammonia

Production
of
Ammonia
Aims
• Explain the conditions in which NO2 can
be formed
• Describe the Ostwald process
Nitric Acid
• Nitrogen is a very unreactive gas.
• Nitric acid (HNO3) is formed when
nitrogen dioxide (NO2), in the presence of
air, dissolves in water.
• The presence of nitrogen oxides in the air,
mean that they will dissolve in rain to
produce a mildly acidic solution. This has
the result that:
– nitrogen compounds are added to the
soil.
– the acidity of the soil will be increased.
• Nitrogen dioxide is produced by the
passage of a high voltage spark through
air since a large amount of energy is
required to break the bonds between the
nitrogen atoms in the molecules.
• These conditions occur when:
– lightning passes through air
– a spark passes in the spark plug of a car
engine
 This does not provide an economic way
of making nitrogen dioxide.
Nitric Acid
• Ammonia normally reacts with oxygen to give
nitrogen and water.
• The combination of nitrogen and oxygen does
not provide an economic industrial route to
nitric acid.
• The catalytic oxidation of ammonia to form
nitrogen dioxide is a step in the industrial
manufacture of nitric acid OSTWALD
PROCESS.
• The catalytic oxidation of ammonia can be
carried out in the laboratory.
The Ostwald Process
Ammonia
Oxygen
Reaction Chamber
(Pt catalyst)
600-900oC
Nitrogen
monoxide
Nitrogen
dioxide
Oxygen
Water
Nitric acid
• This process is carried out at a moderately
high temperature to allow it to proceed
fairly quickly.
• A platinum catalyst is used.
• Since the reaction is exothermic it is not
necessary to continue heating it after the
reaction has started since it will supply
sufficient energy to continue at a
reasonable rate.