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08 Nitrogéncsoport

2016.05.22

Inorganic Chemistry

Nitrogen group

Group V.

 

 

Members of the group:

  • Nitrogen
  • Phosphor

 

Nitrogen (N2)

Structure

  • 1s2 2s2 2p3
  • Diatomic molecule, triple bond

Physical properties

  • Odourless, colourless gas, slightly soluble in water

Chemical properties

  • Nonreactive in normal conditions
  • Lightning (3000 oC): reacts with oxygen, nitrogen oxides are produced

Occurence

  • Atmosphere (78%)
  • Compounds

Importance:

  • Chilling (liquid nitrogen)
  • Ammonia, nitric acid, explosive, fertilizer producing

 

Ammonia (NH3)

Structure

  • Shape: pyramidal (bond angle: 107o)
  • Dipol molecule

Physical properties

  • Colourless gas with a pungent smell
  • Soluble in water (1 l water dissolves 700 l ammonia at room temperature)
  • NH3 + H2O = NH4+ + OH-

Chemical properties

  • NH3 + HCl = NH4Cl
  • 2NH3 + H2SO4 = (NH4)2SO4

Occurence

  • Product of protein decomposition (N-cycle)
  • Urine

Production:

  • N2 + 3H2 = 2NH3

Importance:

  • Nitric acid, explosive, fertilizer, medicine, dye, plastic producing
  • In refrigerators: chilles when evaporates

 

Nitrogen oxides (NOx)

  • N2 + O2 = 2NO
  • 2NO + O2 = 2NO2

 

Nitrogen dioxide (NO2)

  • Reddish-brown poisonous gas
  • Soluble in water:
  • NO2 + H2O = HNO2 + HNO3 (nitrous acid and nitric acid)

 

Dinitrogen monoxide (N2O)

  • Colourless gas with a sweet smell
  • Narcotic (laughing gas)

 

Nitrous acid (HNO2)

  • Blue liquid, occurs in dilute solution only
  • Instable, decomposes:
  • HNO2 = NO2 + NO + H2O
  • Reducing agent: HNO2 ...O… HNO3  

Compounds: nitrites

Importance:

  • Lightning: N-oxides are dissolved in the rain – nitrites and nitrates in the soil

 

Nitric acid (HNO3)

Physical properties

  • Colourless liquid with a pungent smell
  • Stored in dark bottle (decomposes to NO2)
  • Soluble in water:
  • HNO3 + H2O = NO3- + H3O+ (nitrate ion)

Chemical properties

  • Dilute nitric acid: Zn, Fe are dissolved, but Cu is not
  • Concentrated nitric acid: Cu is dissolved, but Fe is not (passive layer on the surface)
  • 4HNO3 + Cu = Cu(NO3)2 + 2NO2 + 2H2O
  • Oxidating agent
  • Választóvíz: az ezüstöt oldja, aranyat nem
  • Királyvíz: salétromsav, sósav 1:3 elegye, ez oldja az aranyat is
  • Xanthoprotein test: yellow colour with proteins
  • HNO3 + NH3 = NH4+ + NO3-
  • HNO3 + NaOH = NaNO3 + H2O

Occurence

  • Compounds: nitrates

Importance:

  • Explosive, fertilizer, medicine, dye, plastic producing

 

Phosphorus (P)

Two allotropes:

 

 

White

Red

Structure

terahedral P4 molecules

Long chains

Physical properties

Yellow-white, soft, solid, insoluble in water, soluble in toluene, oils, fats

Red dust, insoluble in water, toluene, oils, fats

Chemical properties

Flammable at 60oC

 Flammable at 400oC

Poisonous

Not poisonous

 

Chemical properties

  • 2P + 5O2 = P2O5
  • Product: diphosphorus pentaoxide

Occurence

  • Only in compounds: guano, volcanic stones

Importance:

  • Match industry

 

Phosphoric acid (H3PO4)

Preparation:

P2O5 + 3H2O = 2H3PO4

Physical properties

  • Colourless crystal with low melting point
  • Soluble in water
  • H3PO4 + H2O = H3O+ + PO43-
  • Weak acid

Use

  • In dilute solution it is not poisonous, used in soft drinks, preservative as food additive

Phosphates:

  • Trisodium phosphate Na3PO4 („water softener” in detergents)
  • In bones: Tricalcium diphosphate Ca3(PO4)2

Phosphorus cycle in nature