7. Redox

• Oxidation


  Was used for reactions in which oxygen was addedThe losing of electrons via donation
• Oxidation state


  Number of e- gained or lost by an atom during a reaction
• Assigning oxidation states


  - Elements in their standard form/state have an oxidation state of 0 (E.G. F2 is 0)- Elements combined with other elements: Group 1 metals +1Group 2 metals +2F = -1H = +1 (except in metal hydrides .E.G. NaH where this is -1)Oxygen = -2 (except in peroxides where it is -1 and OF2 where it is +2Al = +3Cl = -1 (except in compounds F and O, where it's +ve)In neutral compounds, oxidation states add to give 0
• Reduction


  Oxygen was removed Adding H+The gaining of electrons via acception
• Redox (electron transfer)

  The process by which oxidation and reduction occurs within the same reaction

  
• Half equationsE.G. Cl2 --> Cl-


  Show oxidation and reduction separatelyCl2 + 2e- --> 2Cl-
• 0


  The oxidation state of an uncombined element
• 2-


  The oxidation state of oxygen (other than peroxides where it is 1- and in OF2 where it is 2+)
• 1+


  The oxidation state of any group 1 element
• 2+


  The oxidation state of any group 2 element
• 1-


  The oxidation state of fluorine
• 1-


  The oxidation state of chlorine (other than compounds with F and O)
• 1+


  The oxidation state of hydrogen (other than in metal hydrides where it is 1-)
• 0


  The oxidation state of a stable compound
• Reducing Agent


  An electron donor which reduces another moleculeThis is oxdisedDonates e- to species being reduced
• Define reduced


  Reduction in oxidation statee- gained from another species
• Define oxidised


  Increase in oxidation statee- lost to another species
• Oxidising Agent


  An electron acceptor which oxidises another moleculeThis is reducedAccepts e- from species being oxidised
• Oxidation States


  Values that are used to see what elements have been oxidised and reduced
• Balancing Redox Reactions


  The same number of electrons must be on each side of the equation in order to cancel one another out. Excess hydrogen as allowedMultiply by common factor to recieve an equal amount of e- Join equations togetherCombination of oxidation and reduction half equations
• Balancing Half Equations


  - Balance non oxygen/hydrogen atoms first (specific element, not a compound)- Balance oxygen's by adding H2O- Balance hydrogen's by adding H+ ions- Balance positive charges by adding electrons
• Disproportionation


  The process by which only one element has undergone redox in a single reaction