Single & Double Displacement Reactions

The Activity Series K Na Li Ca Mg Al Zn Fe Ni Sn Pb H Cu Hg Ag Au The Activity Series is used to predict the outcome of single displacement reactions The higher a metal is on the Activity Series, the more likely it will react with those below it A metal will not displace a metal higher on the activity series than itself

The Activity Series Cont. The metals near the top are more reactive because their valence electrons are more easily removed H is the only nonmetal in the series, H2 may be displaced from acids or can be given off when a metal reacts with H2O producing H2 + metal hydroxide

The Activity Series Practice K Na Li Ca Mg Al Zn Fe Ni Sn Pb H Cu Hg Ag Au The Activity Series Practice Which of these will react? K + NaCl  ??? K + NaCl  Na + KCl Al + AgNO3  ??? Al + AgNO3  Ag + Al(NO3)3 Cu + CaCO3  ??? Cu + CaCO3  No Rxn Pb + ZnO  ??? Pb + ZnO  No Rxn

The Solubility Table The Solubility Table is used to predict the outcome of double replacement reactions

The Solubility Table Cont. If both products of a DR reaction are soluble then no reaction occurs If 1+ product of a DR reaction is solid then a reaction occurs

The Solubility Table Practice Which of these will react? NaCl (aq) + Ba3(PO4)2 (s)  ??? NaCl (aq) + Ba3(PO4)2 (s)  Na3(PO4)2 + BaCl2 FeCO3 (s) + CaCl (aq) ??? FeCO3 (s) + CaCl (aq)  FeCl2 (aq) + CaCO3 (s) LiNO3 (aq) + MgBr2 (aq)  ??? LiNO3 (aq) + MgBr2 (aq)  No Rxn Zn(OH)2 (s) + NiSO4 (aq)  ??? Zn(OH)2 (s) + NiSO4 (aq)  ZnSO4 (aq) + Ni(OH)2 (s)

Oxidation/ Reduction Reactions Oxidation and Reduction reactions always take place simultaneously resulting from the gain or loss of electrons. Loss of electrons – oxidation (Increase in Oxidation Number) Ex:Na ------> Na+1 + e-1 Gain of electrons - reduction ( Decrease in Oxidation Number) Cl2 + 2 e-1 ------> 2 Cl-1 LEO says GER

Which substance is oxidized? Oxidation occurs when a molecule does any of the following:    Loses electrons Loses hydrogen Gains oxygen Example: 2Fe2O3 + 3C  4Fe + 3CO2 Which substance is oxidized? If a molecule undergoes oxidation, it has been oxidized and it is the reducing agent . Metals are usually good reducing agents the higher it is on the activity series the better reducing agent it is.

Which substance is reduced? Reduction occurs when a molecule does any of the following: Gains electrons Gains hydrogen Loses oxygen Example: 2Fe2O3 + 3C  4Fe + 3CO2 Which substance is reduced? If a molecule undergoes reduction, it has been reduced and it is the oxidizing agent

zinc is being oxidized while the copper is being reduced. Why?

Oxidation Numbers number assigned to an atom to indicate its degree of oxidation (+) or reduction (-) Rules for Assigning Oxidation Numbers Ions are given the same oxidation number as their charge Oxygen is usually -2 Hydrogen is usually +1 Elemental or diatomic molecules are 0 For compounds the sum of oxidation numbers must equal 0

Steps for Balancing a Redox Reaction: Half Reaction Method In half reaction method, oxidation and reduction half- reactions are written and balanced separately before combining them into a balanced redox reaction. It is a good method for balancing redox reactions because this method can be used both for reactions carried out in acidic and basic medium . S + HNO3  SO2 + NO + H2O Write the unbalanced equation in ionic form Write separate half reactions for the oxidation and reduction processes Balance the atoms in the half reactions Add electrons to one side of each half reaction to balance charge Multiply each half reaction by an appropriate number to make the electrons equal on both sides. S + H+ + NO3-  SO2 + NO + H2O Ox: S  SO2 Red: NO3-  NO Ox: S + 2H2O SO2 + 4H+ Red: 4H+ + NO3-  NO + 2H2O Ox: S + 2H2O SO2 + 4H++ 4e- Red: 4H+ + NO3- + 3e- NO + 2H2O Ox: 3S + 6H2O 3SO2 + 12H++ 12e- Red: 16H+ + 4NO3- + 12e- 4NO + 8H2O

Balancing Redox continued 6. Add balanced ½ equations 7. Add “Spectator Ions” and balance equation Ox: 3S + 6H2O 3SO2 + 12H++ 12e- Red: 16H+ + 4NO3- + 12e- 4NO + 8H2O Total: 3S + 4H+ + 4NO3-  3SO2 + 4NO + 2H2O 3S + 4HNO3- 3SO2 + 4NO + 2H2O

Practice Half-Reactions Don’t forget to determine the charge of each species first! 4 Li + O2  2 Li2O Oxidation Half-Reaction: Reduction Half-Reaction: Zn + Na2SO4  ZnSO4 + 2 Na