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A-Level化学-卤素Halogens

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  Revision: Halogens

  Trends in chemical properties

  chlorine will displace bromine and iodine

  bromine will displace iodine but not chlorine

  iodine will displace neither chlorine or bromine

  Oxidizing Power

  F2>Cl2>Br2>I2

  Reactions with Cl2

  ……

  Reactions with Br2

  ……

  Reactions with I2

  ……

  Trend in electronegativity

  decreases as atomic number increases

  ……

  Trend in boiling point

  all exist as diatomic molecules

  attraction = weak intermolecular forces

  van der Waals forces

  increase with size of molecule

  Tests

  Tests for halide ions

  Reagents

  ……

  Energetics

  Standard enthalpy of formation

  enthalpy change when 1 mol of a compound is formed from its elements under standard conditions

  all reactants and products in their standard states

  Standard enthalpy of combustion

  enthalpy when 1 mol of a substance is completely burned in oxygen

  under standard conditions and all reactants and products in their standard states

  Standard enthalpy of neutralization

  enthalpy change that accompanies the neutralization of an acid by a base to form 1 mol of H2O

  under standard conditions

  Standard conditions

  298 K

  100kPa

  1mol dm-3

  Redox

  Oxidation

  loss of electrons

  addition of oxygen

  Reduction

  gain of electrons

  loss of oxygen

  Reactions which involve both oxidation and reduction

  Oxidizing agent is reduced – an electron pair acceptor

  Reducing agent is oxidized – an electron pair donor

 

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