Nitrogen and Sulphur

• Why is nitrogen unreactive?

  The activation energy to break the nitrogen-nitrogen tiple bond is very high. Nitrogen molecule is polar and does not have any dipoles on it, hence, it is unreactive as it won't attract any electrophiles or neutrophiles.
• Ammonia

  • Ammonia has a higher boiling point than other group 5 hydrides as it can form hydrogen bonding.
  • Ammonia is soluble in water.
  • Ammonia is a weak base as it partially diassociates in water to form hydroxide ions.
• Uses of ammonia

  • Manufacture of fertilisers(Ammonium sulfate, ammonium phospate, ammonium nitrate and urea)
  • Manufacture of nitric acid(Ammonia reacts with oxygen to form nitric acid and water)
  • Manufacture of explosives
• Harmful effects of fertilisers

  • Nitrates from excessive use of fertilizers can seep into ground water and contaminate drinking water.
  • Nitrate ions are poisinous as they can oxidise FE2+ ions to FE3+ ions. Haemoglobin must have iron in its 2+ oxidation state to bind with oxygen so indirectly nitrate ions reduce bodys ability to absorb oxygen.
• Eurtophication

  • Excessive fertilizers washed into ponds, rivers and streams cause the growth of algae and causes algal bloom which blocks sunlight and prevents the aquatic plants from performing photosynthesis. This results in the death of aquatic plants and they get decayed by aerobic bacteria which then uses up the remaining dissolved oxygen and eventually all of aquatic life dies.
• Problems associated with oxides of nitrogen

  • NOx combines with other air pollutants to form oxone which is an eye irritant and causes respiraty problems and headaches.
  • NOx contribute to photochemical smog. It occurs due to the action of sunlight on air pollutants, generating photochemical reactions.
  • Reaction of sunlight with unburnt hydrocarbons and NO2 result in a variety of chemical pollutants like pan and ozone.
  • Other undesriable chemicals like aldehydes also result from this photochemical reaction.
  • They react with unburnt hydrocarbons to form PAN
• Problems with ozone

  • Ozone at ground level is a harmful pollutant.It can create a variety of health problems like chest pain, coughing, throat congestion and irritation. It can cause pneumonia and bronchitis
• Prevention of acidic rain + NOx(1)

  • Fit car exhaust systems with catalytic converters(A catalytic converter converts harmful gases into less harmful gases)
  • Equations for catalytic converter:
  • 2CO + O2 --> 2CO2
  • 2NO + CO--> 2CO2 + N2
  • 2C8H18 + 25O2 --> 16CO2 + 18H2O
• Prevention of acidic rain + NOx(2)

  • Burn less sulfur containing fossil fuels in power stations and run power stations that burn fossil fuels at a lower temperature so that less sulfur dioxide is produced.
  • Treat exhaust gases from power stations and other gases with lime(CaO). CaO +SO2 --> CaSO3. This process is known as flue gas desulfurisation.
• Effects of acid rain on environment

  • Corrosion of limestone structures, buildings and statues.
  • Corrosion of steel structures because the iron present in steel reacts with acid
  • Acidification of lakes and agricultural lands
  • Deforestation
• Uses of sulfuric acid

  • Manufacture of paints, fertilisers and dye
  • Manufacture of explosives
  • Tanning of leather
  • Used as an electrolyte in car batteries
  • Used in removal of rust from iron and steel objects
• Uses of sulfur dioxide

  • Sulfur dioxide is a good reducing agent and it therefore prevents food from getting oxidised (Used in food preservation)
  • It inhibits growth of bacteria and prevents food from decaying
  • It is used to prevent food from over ripening
  • It is used to preserve wine as it prevents alcohol from getting oxidised to carboxylic acids.