12. Nitrogen And Sulfur. Flashcards
Why is nitrogen gas so unreactive?
Nitrogen atoms form triple covalent bonds between two nitrogen atoms and the bond enthalpy of the nitrogen triple bond is 1000kJ /mole. So this means 1000kJ/mole is required to break one mole of N2 triple bond. Due to this difficulty to break the bond nitrogen and oxygen in air will not react with each other. It is a non polar molecule so is not attracted to or likely to react with other molecules.
How is ammonia made?
In the haber process
N2 (g) + 3H2 (g) -<> 2NH3 (g)
250atm pressure
450 degrees Celsius
Iron catalyst
Describe and explain the basicity of ammonia
Ammonia can act as a bronsted Lowry base by accepting a proton H+ using the lone pair of electrons on the nitrogen atom to form an ammonium ion.
Describe and explain the structure and formation of an ammonium ion formed?
By an acid base reaction of ammonia with water.
The nitrogen in ammonia is covalently bonded to three hydrogen atoms and has one lone pair of electrons causing the ammonia molecule to have a pyramidal shape.
Ammonium ion has a tetrahedral shape.
Describe and explain the displacement reaction of ammonia from ammonium salts
Ammonium chloride and calcium hydroxide are mixed together and then heated.
NH4+ acts as an acid and OH- acts as a base
the strong base displaces ammonia by pulling the proton away from the ammonium ion, effectively converting it back to ammonia gas.
State the natural occurrence of nitrogen oxides- (equations?)
Lightening can trigger the formation of NO and NO2.
N2 (g) + O2 (g) → 2NO(g)
N2 (g) + 2O2 (g) → 2NO2 (g)
State and explain the man made occurrences of nitrogen oxides
Under high pressure and temperature in the car engine nitrogen can react with oxygen to form nitrogen oxides. These oxides are released into the atmosphere through the car’s exhaust fumes
State and explain the catalytic removal of nitrogen oxides.
Cars are fitted with catalytic converters to reduce the pollutants from motor vehicles. Nitrogen oxides are reduced on the surface of the hot catalyst to form the unreactive and harmless nitrogen gas.
2CO(g) + 2NO(g) → 2CO2 (g) + N2 (g)
what are VOC’s (volatile organic compound)
Primary pollutant in exhaust fumes from unburnt hydrocarbons from fuel and their oxidized products in exhaust fumes
Explain how PAN is formed and what it is
It is a secondary pollutant found in photochemical smog
VOC’s react with nitrogen oxides in air to form peroxyacetyl nitrate (PAN)
Describe the formation of acid rain
Lightning strikes trigger the formation of NO and NO2 and the air also contains oxygen and water droplets that make up clouds. The NO2 dissolves and reacts in water with oxygen.
4NO2 + 2H2O + O2 ——> 4HNO3
The clouds rise and droplets get larger. Then the droplets with HNO3 which are heavy enough will fall as acid rain.
Describe the role of nitrogen oxides as catalysts
NO2 catalyses the oxidation of SO2 to SO3
NO2 + SO2 ——> SO3 + NO
SO3 then reacts with rainwater to form dilute sulfuric acid
SO3 + H2O —-> H2SO4
