Ugrás a tartalomhoz Lépj a menübe
 


07 Oxigéncsoport

2016.02.21

Oxygen group

 

 

  • Group VI.

Members of the group:

  • Oxygen
  • Sulphur
  • Selene

 

 

Oxygen

Structure:

  • 1s2, 2s2, 2p4
  • 2 unpaired electrons – double bonds, biatomic molecule (O2, O=O)

Physical properties

  • Colourless, inodorous gas
  • A bit soluble in water (water amimals’ breathing)

Chemical properties:

  • Oxidating agent – needs 2 electrons to have noble gas structure
  • Oxidation is exoterm!
  • 2Mg + O2 = 2MgO
  • 2C + O2 = 2CO
  • C + O2 = CO2
  • CH4 + 2O2 = CO2 + 2H2O

Compounds of Oxygen: oxides

Occurence:

  • As an element: in atmosphere (21%)
  • In compounds: water, rocks

Importance:

  • Breathing - photosynthesis
  • Industry: high-temperature flames (welding)

Producing: water electrolysis, air condensation

 

 

 

Ozone

Allotrope of oxygen

Structure:

  • Triatomic molecule (O3)
  • V-shaped molecule, delocalised π-bond

Physical properties

  • Colourless, poisonous gas with distinctive odour

Chemical properties:

  • Strong oxidating agent

Formation:

  • In nature: UV radiation, lightning
  • O2 = O + O
  • O2 + O = O3
  • Artificially: sun lamps, copiers, air pollution (nitrogen oxides, exhaust gases of cars, spark plugs)

Occurence:

  • In atmosphere between 15 and 35 km of altitude (ozone layer)

Importance:

  • Absorbs cosmic UV rays

 

 

 

Compounds of oxygen

Water

Structure:

  • V-shaped dipole molecule (H2O)
  • Bond angle: 105o
  • Hydrogen bonds between the molecules

Physical properties

  • Colourless, odourless liquid
  • Largest density at 4oC
  • Large specific heat capacity (thermoregulation, heating)
  • Large surface tension

Chemical properties

Reaction with halogens

  • Cl2 + H2O = HCl + HOCl

Reaction with  „s” block metals

  • 2Na + H2O = 2NaOH + H2

Corrosion

  • Fe + H2O + O == FeO(OH)

At higher temperature:

  • C + H2O = CO +H2

With nonmetal oxides:

  • CO2 + H2O = H2CO3

With metal oxides:

  • CaO + H2O = Ca(OH)2

Amphoteric substance (can be a base and an acid, too)

  • HCl + H2O = Cl- + H3O+
  • NH3 + H2O = NH4+ + OH-
  • H2O + H2O = H3O+ + OH-
  • Neutral substance [H3O+] = [OH-]

Occurence: In nature in gas, solid and liquid state

Importance:

  • Good solvent (ions and polar molecules) (salt water, freshwater, acid rain, cave formation)
  • Necessary for life (solvent, takes part in reactions, place of reactions, thermoregulation), water content 60-99%
  • Thermal water

 

Hydrogen peroxide

Structure:

  • H-O-O-H, H2O2

Physical properties

  • Colourless, odourless liquid

Chemical properties

  • Unstable, decomposes
  • H2O2 = H2O + O2 (bubbles)
  • Strong oxidizer

Importance:

  • Bleaching agent (textiles, hair) and disinfectant

 

 

Sulfur (S)

Structure

  • Only single bonds (more shells, less electronegativity)
  • 8-atomic molecules, molecular lattice (weak interaction)

Allotropes:

  • Crystallic, amorph

Physical properties

  • Yellow, solid fragile crystal with low melting point
  • Insoluble in water, soluble in toluene, carbon disulfide

Chemical properties

  • Zn + S = ZnS
  • Fe + S = FeS
  • Hg + S = HgS
  • H2 + S = H2S

Occurence

  • As an element (volcanic regions), in compounds (sulfides)

Importance:

  • Production of sulfuric acid, rubber, pesticides, dye, cosmetics

 

 

Hydrogen sulfide (H2S)

Structure

  • V-shaped molecule, no H-bonds

Physical properties

  • Colourless gas
  • Odour: faint rotten egg
  • Poisonous
  • Slightly soluble in water (weak acid)
  • H2S + H2O = H3O+ + HS-

Chemical properties

  • H2S + O2 = H2O + SO2
  • Mixture is explosive!

With less oxygen:

  • H2S + O2 = H2O + S
  • 2H2S + O2 + 4Ag = 2Ag2S + 2H2O

Reducing agent:

  • H2S + Br2 = 2HBr + S
  • H2S + 2NaOH = Na2S +2 H2O

Occurence

  • Volcanic gases
  • Hot springs
  • Decomposition of proteins

Importance:

  • Reagent in laboratory
  • Poisonous! (joins to the hemoglobine!)

 

 

Sulfur dioxide (SO2)

Structure

  • V-shaped molecule, double bonds

Physical properties

  • Colourless gas with a pungent, irritating, and rotten smell
  • Poisonous
  • Soluble in water
  • SO2 + H2O = H2SO3

Occurence and importance

  • Volcanic gases
  • Acid rain

 

 

Sulfurous acid (H2SO3)

  • Reducing agent
  • Bleach (canning industry)
  • Disinfectant (wine-making)
  • Salts: sulfites

 

 

Sulfur trioxide (SO3)

Production:

  • 2SO2 + O2 = 2SO3

Structure

  • Trigonal planar molecule, double bonds

Physical properties

  • Colourless liquid with quite high density and viscosity (polymerisation!)
  • Soluble in water
  • SO3 + H2O = H2SO4

 

 

Sulfuric acid(H2SO4)

Physical properties

  • Colourless liquid with quite high density (ρ = 1.8 g/cm3) and viscosity
  • Soluble in water (exothermic reaction!)
  • H2SO4 + 2H2O = 2H3O+ + SO42-
  • Strong acid
  • Hygroscopic

Chemical properties

  • Oxidating agent
  • C12H22O11 (+H2SO4) == 12C + 11H2O
  • Dilute sulfuric acid reacts with metals (except copper)
  • H2SO4 + Zn = H2 + ZnSO4
  • H2SO4 + Fe = H2 + FeSO4
  • Concentrated sulfuric acid: Al, Fe can not be dissolved (passive layer on the surface)
  • Salts: sulfates

Use

  • Accumulators, fertilizer, dye, explosive, leather industry
  • Compounds: gypsum (CaSO4·2H2O), Copper (II) sulfate (CuSO4·5H2O)