NITROGEN AND ITS COMPOUND

Outcomes of learning

• Understand the Inert nature of Nitrogen • Principle of Nitrogen extraction from air • Manufacture of Ammonia gas using Haber

Process• Properties and uses of Ammonia gas to

manufacture Nitric Acid and Fertilisers• Name and draw the different oxides of

Nitrogen (NO, NO2, N2O4)

• Understand the formation of smog and destructive effects of acid rain

• Know the functions of catalytic converter used in car exhausts

• Nitrogen cycle

Keep Quiet

WHAT IS NITROGEN ?

• Nitrogen, N2 is a Diatomic gas • Makes up 78% of the atmosphere• Colorless, Tasteless, and Odorless

Properties

• Nitrogen – one of the most electronegative elements ( exceeded by Oxygen and Fluorine only )

• Nitrogen molecule consists of TRIPLE BONDS (N≡N)

• Extremely short inter nucleus distance • Very high bond energy • Chemically Inert due to strong N≡N bond • Dissociation energy is 940kJ mol ¹ˉ

Shapes of Nitrogen

• N≡N is LINEAR in shape • Each nitrogen shares 3 valence electrons, with

a lone pair on each side of the atom.• The shape is symmetrical and thus the non-

polar nature of the nitrogen molecules

Where to find Nitrogen ?

• Plants – In nitrates form from the soil to make protein

• Animals – they consume the plants to get protein supplies

Extraction of Nitrogen from Atmosphere

• Fractional Distillation

• In 2 stages,– Clean air ( after removal of dust particles and

carbon dioxide ) into a compressor -> compressed under high pressure and low temperature until liquefied -> Left only Nitrogen and Oxygen gas in the liquid air

• After that, the mixture of liquid air undergoes Fractional Distillation.

• Nitrogen gas collected before oxygen.• Because Nitrogen has lower boiling point than

oxygen.• -196 °C Nitrogen• -182.95 °C Oxygen

Compounds of Nitrogen

• Electronic Configuration of Nitrogen 1s²2s²2p³

Compounds of Ammonia

• Produced by Haber Process

• Hydrogen and Nitrogen mixed in ratio 3:1 by volume.

• Gases are dried and passed over finely divided iron catalyst at 450° C and pressure of 250 atm

Properties of Ammonia• Colorless• Pungent smelling gas• Boiling point of -34 °C• Poisonous• Does not burn in air• Most soluble and the only common alkaline gas

Nitric Acid

• Ostwald Process• Manufactured by catalytic oxidation of

Ammonia

How ?

• The ammonia and air are passed over a platinum gauze at 700-800 °C. Its oxidised to Nitric acid

• The hot nitric oxide gas is cooled and then oxidised by more air to nitrogen dioxide

• The Nitrogen Dioxide are dissolved in water to form nitric acid under conditions of 80 °C and 8 atm

To get a higher yield,

• The purity of nitric acid produced is approx. 60%.

• Higher concentration of Nitric Acid can be obtained by distillation with concentrated Sulphuric acid where the purity can be increased to as high as 98%

Uses of Nitric Acid

• To produce Ammonium Nitrate and Sodium Nitrate for fertilisers

• To Produce Chemical Explosive for mining and quarrying and war as well. HAHA

• Trinitoglycerine, TNT/ Trinitrotoluene• As strong oxidising agent• As an acid. Only very dilute acid will give off

hydrogen gas with electropositive metals

Oxides of Nitrogen

• Nitric Oxide, NO is produced when Nitrogen gas and Oxygen gas in the atmosphere combine at high temperature (during thunderstorms and lightning)

• Also produced in hot car engines

Properties of Nitric Oxide

• Colorless• Toxic and Insoluble in water• The nitrogen atom in nitric oxide has 7

electrons in its outer orbital. Due to the add number of electrons, nitric acid is unstable and easily be oxidised to Nitrogen Dioxide, NO2

Nitrogen Dioxide

• Brown and toxic gas• At room temperature, it has a V-shape• Has tendency to form dimers, dinitrogen

tetroxide, N2O4 which is a colorless gas.

Pollution caused by Nitric Oxide

• Considered as primary air pollutant• -Burning of fossil fuels • -Reaction between internal combustion

engines at high temperatures• Lightning which combines the atmospheric

nitrogen and oxygen

• When exposed to air, NO is oxidised to NxOy to form nitrous acid and nitric acid (acid rain) where these are considered as second pollutant.

• Also tend to combine with gaseous hydrocarbons in the atmosphere to form smog.

Acid Rain

• Produced in nature when carbon dioxide gas from the armosphere dissolves in rainwater to form carbonic acid. H2CO3

• Also produced when sulphur dioxide gas comes into contact with rainwater to form sulphuric acid.

Cons of Acid Rain

• Cause damages to marble and limestone of buildings and statues. Also harmful to vegetation and aquatic lives, eg. Octopus

Photochemical Smog

• SMOG – used to describe a smoky and cloudy situation when smoke from automobile exhaust and fog combines in the presence of sunlight

SMOG

• Nitric Oxide is the product between atmospheric oxygen and nitrogen in an internal combustion engine at very high temperatures.

• This reaction is Ozonolysis and can cause rubber tyres of automobile to crack

• Also harmful to health as it damages lung tissues

Catalytic Converter

Where is the catalytic converter ?

1, 2, 3, 4, 5 or 6 ?

1. Exhaust Manifold2. Catalytic Converter 3. Midbox/ Bullet4. Muffler 5. Tailpipe 6. Flow pipe

Cat-con

• Consists of catalysts like platinum, palladium and rhodium.

• Hot exhaust gas are passed over the 1st chamber with these catalysts to oxidise carbon monoxide and unburned hydrocarbons to carbon dioxide and water. While nitric oxide and nitrogen dioxide are reduced to harmless nitrogen and oxygen gases.

• In the 2nd chamber, CuO or Cr2O3 are used to dissociate nitric oxide to form harmless nitrogen and oxygen gases.

• By coating platinum catalyst on car radiators and air conditioner compressors, the air that flow through the engines can be purified by converting ozone and carbon monoxide to harmless carbon dioxide and oxygen gases.

• O3 + CO O2 + CO2

Nitrogen Cycle