Introduction to Oxidation and Reduction IB Chemistry Text Green and Damji TEXT 9.1 & 9.2 Copyright © The McGraw-Hill Companies, Inc.  Permission required for reproduction or display.

Types of Chemical Reactions ? type of reaction ? Mg(s) + 2 HCl (aq)  MgCl2 (aq) + H2 (g) 2. Pb(NO3)2 (aq) + 2 NaI (aq)  PbI2 (s) + 2 NaNO3 (aq) 2 H2O2 (aq)  O2 (g) + 2 H2O (g) 2 O2 (g) + CH4 (g)  CO2 (g) + 2 H2O (g) 5. 2 H2 O (g)  O2 (g) + H2(g)

another way to classify Types of Chemical Reactions A. Acid Base Reactions B. Precipitation Reactions C. Redox Reactions CaO (s) + 2 HCl (aq)  CaCl2 (aq) + H2O (l) H3PO4 (aq) + 3 NaOH (aq)  Na3PO4 (aq) + 3 H2O (l) Pb(NO3)2 (aq) + 2NaI (aq) PbI2 (s) + 2NaNO3 (aq) which can be shortened to…Pb2+ + 2I- PbI2 (s) 2 Zn (s) + I2 (s) ZnI2 (aq) 2 Zn (s) + I2 (s) Zn2+ (aq) + 2 I- (aq)

Classify the following reactions as AB/PPT/RedOx Ca2+ + CO32- CaCO3 ________________ NH3 + H+ NH4+ ________________ Zn + 2HCl ZnCl2 + H2 ________________ Ca + F2 CaF2 ________________ 4.4

Oxidation-Reduction Reactions (electron transfer reactions) 2Mg + O2 2MgO What is happening in this reaction? oxidation – loss of electrons: reduction – gain of electrons: 4.4

Helpful Mneumonics LEO the lion goes GER Loss of Electrons is Oxidation Gain of Electrons is Reduction OIL RIG Oxidation is the Loss of electrons Reduction is the Gain of electrons

Oxidation number Na, Be, K, Pb, H2, O2, P4 = The charge the atom would have in a molecule (or an ionic compound) if electrons were completely transferred to the more electronegative element. Free elements (uncombined state) have an oxidation number of zero. Na, Be, K, Pb, H2, O2, P4 = In monatomic ions, the oxidation number is equal to the charge on the ion. Li+, Li = ; Fe3+, Fe = ; O2-, O = The oxidation number of oxygen is usually . In H2O2 and O22- it is . 4.4

HCO3- O = ____ H = ____ 3x(-2) + 1 + ? = -1 C = ____ The oxidation number of hydrogen is____except when it is bonded to metals in binary compounds. In these cases, its oxidation number is____. Group 1 metals are____, Group 2 metals are____and fluorine is always____. 6. The sum of the oxidation numbers of all the atoms in a molecule or ion is equal to the charge on the molecule or ion. 7. Oxidation numbers do not have to be integers. Oxidation number of oxygen in the superoxide ion, O2-, is ____. HCO3- Oxidation numbers of all the elements in HCO3- ? O = ____ H = ____ 3x(-2) + 1 + ? = -1 C = ____ 4.4

The oxidation numbers of elements in their compounds The periodic table in your planner includes the most common oxidation numbers! 4.4

I F7 F = ____ 7x(____) + ? = 0 I = ____ K2 Cr2 O7 Na I O3 Na = ____ What are the oxidation numbers of all the elements in the following compounds ? F = ____ 7x(____) + ? = 0 I = ____ K2 Cr2 O7 Na I O3 Na = ____ O = ____ O = ____ K = ____ 3x(____) + ____ + ? = 0 7x(__) + 2x(__) + 2x(?) = 0 I = ____ Cr = ____ 4.4

More to know… An increase in oxidation number is oxidation. A decrease in oxidation number is reduction. The substance that is oxidized (loses e-; ox # increases) is called the reducing agent. The substance that is reduced (gains e-; ox # decreases)

Zn (s) + CuSO4 (aq) ZnSO4 (aq) + Cu (s) ox: red: --------------------------------------- ttl: ____ is oxidized - is reducing agent ____ is reduced - is oxidizing agent 4.4

Copper wire reacts with silver nitrate to form silver metal. What is the oxidizing agent in the reaction? ox: red: --------------------------------------- ttl: ____ is oxidized - is reducing agent ____ is reduced - is oxidizing agent 4.4

Types of Oxidation-Reduction Reactions Combination Reaction (aka Synthesis) A + B C +3 -1 2Al + 3Br2 2AlBr3 Decomposition Reaction C A + B +1 +5 -2 +1 -1 2KClO3 2KCl + 3O2 4.4

Types of Oxidation-Reduction Reactions Combustion Reaction A + O2 B +4 -2 S + O2 SO2 2Mg + O2 2MgO +2 -2 4.4

Types of Oxidation-Reduction Reactions Single Displacement Reaction A + BC AC + B +1 +2 Sr + 2H2O Sr(OH)2 + H2 Hydrogen Displacement +4 +2 TiCl4 + 2Mg Ti + 2MgCl2 Metal Displacement -1 -1 Cl2 + 2KBr 2KCl + Br2 Halogen Displacement 4.4

Types of Oxidation-Reduction Reactions Disproportionation Reaction Element is simultaneously oxidized and reduced. +1 -1 Cl2 + 2 OH- ClO- + Cl- + H2O Chlorine Chemistry 4.4

Chemistry in Action: Metals from the Sea Redox or not? CaCO3 (s) CaO (s) + CO2 (g) _______________ CaO (s) + H2O (l) Ca2+ (aq) + 2OH (aq) - _______________ Mg2+ (aq) + 2OH (aq) Mg(OH)2 (s) - _______________ ____________ Mg(OH)2 (s) + 2HCl (aq) MgCl2 (aq) + 2H2O (l) _______________ MgCl2 (aq) Mg (s) + Cl2 (g) Write half reactions for one of the redox reactions above: ox: red: