C5- Chemicals in the Atmosphere

Dry air is a mixture of
1. 78% Nitrogen
2. 21% Oxygen
3. 1% Argon
4. 0.04% Carbon Dioxide
5. made of molecular substances
  1. low melting and boiling points
  2. held together by very strong covalent bonds
    1. but have weak forces of attraction
  3. pure ones don't conduct electricity as molecules aren't charged. No free electrons or ions to move.
Covalent bonding is sharing electrons with atoms
1. each one provides one extra shared electron for each atom
  1. both atoms have a full outer shell
  2. each atom involved has to make enough covalent bonds to fill up its outer shell
2. atoms bond due to electrostatic attraction
  1. between the positive nuclei & the negative electrons shared between them
Hydrosphere
1. contains compounds that can be dissolved
  1. ionic compounds called salts -why the sea is 'salty'
    1. sodium chloride - NaCl2
    2. magnesium chloride - MgCl2
    3. potassium bromide - KBr
    4. made up of charged ions
      1. ions with opposite charge are strongly attracted to one another.
        giant lattice formed
        very ionic bonds between all the ions
    5. high melting and boiling points as the forces of attractions are very strong
    6. conducts electricity when dissolved
      1. ions separate and are free to move
        able to carry electric current
identifying positive ions
1. sodium - orange/yellow flame
  1. potassium - lilac flame
    1. calcium - brick-red flame
      1. copper - blue-green flame
2. add sodium hydroxide to metal hydroxide to form a precipitate
  1. Calcium, Ca 2+ // white precipitate // Ca2+(aq)+2OH-(aq) = Ca(OH)2 (s)
    1. Copper (II), Cu2+ // blue precipitate //Cu2+(aq)+2OH-(aq)= Cu(OH)2 (s)
      1. Iron (II) Fe2+ // green precipitate // Fe2+(aq)+2OH- (aaq) = Fe(OH)2 (s)
        Iron (III) Fe3+ // reddish precipitate // Fe3+(aq)+3OH-(aq) = Fe(OH)3 (s)
        ionic equation (half equation)
        Ca2+(aq)+2OH-(aq) = Ca(OH)2 (s)
identifying negative ions
1. hydrochloric acid can help detect carbonates
2. sulfates identified with hydrochloric acid and barium chloride
3. halides identified by nitric acid and silver nitrate
lithosphere
1. Earth's rigid outer layer (crust and a bit of mantle)
  1. made up of a mixture of minerals, silicone, oxygen and alumnium
2. carbon forms giant covalent structure
  1. diamond -four covalent bonds, hard substance, high melting point, does not conduct electricity, insoluble
  2. graphite - three covalent bonds, soft substance, high melting point, conducts electricity (lose electrons/ions to move), used for electrodes
metals from minerals
1. metal ore - compound in lithosphere. rock containing enough metal to economic
  1. iron ore - haematite
  2. copper ore - chalcopyrite
  3. some metals can be extracted by carbon reduction
    1. 2Fe2O3 (s) + 3c (s) = 4Fe(s) + 3Co2 (g) iron (III) oxide + carbon = iron + carbon dioxide
      1. when a metal oxide loses its oxygen it is REDUCED
  4. finite resource
    1. recycling
electrolysis
1. decompisition of a substance using electricity
  1. liquid needed (electrolyte) needed to conduct electricity
    1. electrolytes usually free ions dissolved in water or molten ionic compound
      1. free ions conduct electricity
        flow of electrons allow complete eletrical circuit
  2. electrons are taken away from ions at the positive electrode and given to other ions at the negative electrode
    1. as ions gains or lose electrons they become atoms or molecules
calculating masses
1. Ar = relative atomic mass
  1. Mr = relative formula mass
    1. MgCl2 - Mg (24) Cl2 (35.5x2) =95
    2. Mg(OH)2 - Mg(1x24)+(16+1)x2=58
  2. C = 12
2. atom relative mass
  1. mass of metal in the ore
    1. mass metal / relative formula mass
      1. multiply by the mass of compound
metal
1. metallic bonds involve free electrons
  1. come from outer shell of every metal atom in the structure
    1. positively charged metal ions are held together by a sea of free electrons
      1. good conductors of heat and electricity
      2. strong and malleable
      3. high melting and boiling points

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C5- Chemicals in the Atmosphere

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