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3. Oxigéncsoport

2017.01.07

Oxygen group

 

 

  • Group VI.

Members of the group:

  • Oxygen
  • Sulphur
  • Selene

 

 

Oxygen

Structure:

  • 6 electrons on the outer shell
  • 2 unpaired electrons – double bonds, biatomic molecule (O2, O=O)

Physical properties

  • Colourless, inodorous gas
  • Slightly 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 the atmosphere (21%)
  • In compounds: water, rocks

Importance:

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

Producing: water electrolysis, air condensation

 

 

 

Ozone

 

Structure:

  • Triatomic molecule (O3)

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
  • Disinfectant

 

 

 

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

Occurence: In nature in gas, solid and liquid state

Importance:

  • Good solvent (salt water, freshwater, acid rain, cave formation)
  • Necessary for life (solvent, thermoregulation), body water content 60-99%
  • Fresh water: less amount of dissolved salts
  • Salt water: seas, oceans
  • Thermal water
  • Acid rain: gases are dissolved in rain (harmful for plants, animals, buildings)

 

Hydrogen peroxide

Structure:

  • H-O-O-H, H2O2

Physical properties

  • Colourless, odourless liquid

Chemical properties

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

Importance:

  • Bleaching agent (textiles, hair) and disinfectant

 

 

Sulfur (S)

Structure

  • 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

Occurence

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

Importance:

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

 

 

 

Sulfur dioxide (SO2)

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)

 

 

Sulfur trioxide (SO3)

Production:

  • 2SO2 + O2 = 2SO3

Properties

  • Soluble in water
  • SO3 + H2O = H2SO4

 

 

Sulfuric acid(H2SO4)

Physical properties

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

Chemical properties

  • Oxidating agent
  • Dilute sulfuric acid reacts with metals (except copper)
  • Salts: sulfates

Sulfuric acid on your skin:

  1. wipe with a dry cloth
  2. wash with large amount of water for at least 10 minutes
  3. neutralize with sodium bicarbonate

Use

  • Accumulators, fertilizer, dye, explosive, leather industry
  • Compounds: gypsum (calcium sulphate), Copper (II) sulfate