Chemistry Unit 2 Checklist 6CH02 Applications of Core Principles of Chemistry

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Shapes of Molecules

  • Wedge =  Coming out 
  • Dashed line = Going behind
  • Trigonal bipyramidal angles = 120 and 90 1 dash 1 wedge 3 normal
  • Wedge and dashed at 120
  • Octrahedral 2 dashed 2 wedged 2 normal 90 degrees

Intermolecular forces

  • Van der waals = Both Permenant and induced dipole forces so must define which your talking about when you use it.
  • Instaneous Induced Dipole forces = London Forces=Dispersion Forces
  • H bonding only happens with H and small+electronegative atom
  • Strongest: F>O>N>C :Weakest
  • H bond is 180 degrees
  • Ice Less dense then water as in ice rings of 6 H2O molecules which H bond and the distance is larger than when the ice melts into water as the ring structure is destroyed
  • DNA = Double helix each strand is held to together by H bonds 
  • Adenine Thymine 2 H bonds Guanine and Cytosine 3 H Bonds
  • Sublimation = when a solid turns straight into a gas without melting

Redox

Ability to reduce another molecule depends on high easily the molecule itself can lose electrons eg iodine is a strong reducing agent whereas fluorine isn't.

On the other hand Oxidising ability depends on how easily it can be reduced itself so fluorine is a strong oxidising agent as it can easily gain elctrons due to high electronegativity.

Solubility

  • Solute particles must be seperated from each other and must be surronded by solvent particles
  • Solvent-Solute forces must be stronger than Solvent-Solvent and Solute-Solute
  • Like disolves like, so a polar substance disolves in another polar substance
  • If mixture of both polar and non polar areas eg an alcohol solute must contain both polar and non polar bonds.
  • Group 2 hydorxides solubility increases down group Berylium doesnt disolve.
  • Sulfates decrease down group Barium sulfate is insoluable.

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