Chapter 13 – oxidation and reduction



ElectrochemistryChapter 13 – oxidation and reductionOxidation:Formerly known as the reaction of substances with oxygen, it is now known as the loss of electrons of a molecule, atom or ion in a chemical reaction 4 Fe(s) + 3 O2(g) 2 Fe2O3(s)Fe?: goes from the atom state (zero charge) to ion (+3) charge, thus loosing 3 electrons.Oxidizing agent is what get reduced in a reaction. It is what facilitates the reduction. In the rust reaction, it is the oxygen which goes from its atomic state (zero charge) to its ion state (2-) in the rust. It facilitated the reduction by picking up the extra electrons.Reduction?: Formerly known to be the production of metals from their compounds, it is now known as the gain of electrons of a molecule, atom or ion in a chemical reactionSnO2(s) + C(s) Sn(s) + CO2(g)Sn: goes from the (4+) ions to the tin atom (zero charge). Thus the gain of 4 electrons.Reducing agent is what get oxydized in a reaction. It is what facilitates the oxydation. In the tin reaction, it is the carbon which goes from its atomic state (zero charge) to its ion state (4+) in the carbon dioxyde. It facilitated the oxydation by donating the extra electrons.010160In all reactions both oxidation and reduction must occur. One to donate electrons, one to accept the electrons.In all reactions both oxidation and reduction must occur. One to donate electrons, one to accept the electrons. Ex:Cu(s) + Br2(l) CuBr2(s)Cu: Goes from atom (0) to Ion (2+). Lost 2 e-. Oxydization, thus is the reducing agent.Br2: Goes from atom (0) to Ion (1-). Gain 1 e-. Reduction, thus is the oxydizing agent.Practice 13.1 pg559 #1-6Half Reactions:In a chemical reaction the componants can be broken into a few categories:Oxidizing agentsReducing agentsSpectatorsTo see the reduction and oxidization more clearly, ? reactions are used. Spectator ions are not shown in the half reactions.4 Fe(s) + 3 O2(g) 2 Fe2O3(s)Oxidation: Fe(s) Fe3+(aq) + 3e-Reduction: O2(g) + 2e- 2 o2-(aq)SnO2(s) + C(s) Sn(s) + CO2(g)Oxidation: C(s) C4+(aq) + 4e-Reduction: Sn4+(aq) + 4e- Sn(s)Spectator: O2-(aq)Practice: Page 564 #7-11Complex Half Reaction Equations:Some reactions, particularly those with polyatomic ions, undergo reactions in acidic or basic solutions. The presence of water, hydrogen ions, and hydroxide ions play a part in the reactions.In an acidic solution, hydrogen ions are on the reactant side of the equation. To balance this, water molecules are added to the products side.Add water to balance the oxygens in the reactionAdd hydrogens to balance the new hydrogens from the waterAdd electrons to balance the charge from the hydrogen ionsIn a basic solution, hydroxide ions are on the reactant side of the equation. They are also added to the product side of the equation, but in combination with the hydrogen ions they turn into water.Add water to balance the oxygenAdd hydrogens to balance the hydrogens from the waterAdd hydroxides to each side of the equation to cancel the hydrogen ionsCancel equal waters from each sideAdd elections to balance the excess charge313182013970000Ex: Acidic HNO2(aq) NO(g)HNO2(aq) NO(g) + H2O(l)H+(aq) + HNO2(aq) NO(g) + H2O(l)e- + H+(aq) + HNO2(aq) NO(g) + H2O(l)Ex: BasicCu(s) CuO(s)H2O(l) + Cu(s) CuO(s) H2O(l) + Cu(s) CuO(s) + 2 H+(aq) 2 OH-(aq) + H2O(l) + Cu(s) CuO(s) + 2 H+(aq) + 2 OH-(aq)2 OH-(aq) + H2O(l) + Cu(s) CuO(s) + 2 H2O(l)2 OH-(aq) + Cu(s) CuO(s) + H2O(l) 2 OH-(aq) + Cu(s) CuO(s) + H2O(l) + 2 e-Practice: Page 566, # 12 Page 567 #6, 7 ................
................

In order to avoid copyright disputes, this page is only a partial summary.

Google Online Preview   Download