# Oxidation and Reduction - CVUSD Home Oxidation and Reduction Chapter 20 Day 1 INTRO TO REDOX Definition A reaction in which electrons are transferred from one substance to another Oxidation cannot occur without reduction

Oxidation: 1. Losing of electrons 2. Increasing the oxidation charge (0 to +1 or -2 to -1) Reduction 1. Gaining of electrons 2. Reducing the oxidation charge (-1 to -2 or 1 to 0) Oxidation Numbers Number of charges the atom would have in a molecule if electrons were transferred completely Rule #1

Oxidation number of a free element is zero Example: Mg, H2, Na, P4, S8, K Rule #2 Oxidation number of an ion is the charge of the ion Example: Mg2+, O2, Al3+, Br Rule #3 Oxidation number for H is +1 when bonded to a nonmetal *Exception: when bonded to a metal it is 1 Example: HCl, HF, LiH, H2O, NaH, MgH2

Rule #4 Oxygens oxidation number is 2 *Two Exceptions: peroxides and fluorine Example: H2O2 OF2 Practice 1. HNO3

1. K3PO4 2. NO3 2. CaSO4 3. MgCl2 3. SiCl4 4. CO32

Whiteboard Practice 1. Give the oxidation # of the nitrogen atom: a. N2 a. N2O4 a. NO2 b. NO b. N2O5 b. NH4+ 2. Determine the oxidation # of the sulfur atom

a. H2S a. H2SO4 a. HS g. SO2 b. SO2 b. S b. S22 3. Indicate the oxidation # of phosphorus in each: a. HPO3 a. H3PO3 a. H4P2O7 b. H3PO2

b. H3PO4 b. H5P3O10 Day 2 REACTIONS Redox Reaction 2 Mg + O2 2 MgO

Oxidation Reaction When an electron is lost (electrons appear as products) X0 X+1 + e Oxidation # goes up Reduction Reaction When an electron is gained (electrons appear as reactants) e + Y+1

Y0 Oxidation # goes down Ways to Remember L E O goes G E R O L X S E I E C D T A

R T O I N O S N A I N L E

C T R O N S E D U C

T I O N OIL X S O S I I D

N A G T I O N RIG E S A

D I U N C I T N I G O

N Examples: Ex1 Na0 Ex2 Fe+3 Na+1 Fe+2

Ex3 N+1 N+2 Ex4 Mg+2 Mg0 Day 3 REDOX REACTIONS

Example 1: HCl + Zn ZnCl2 + H2 Example 2: Mg + N2 Mg3N2 Example 3: H2S + Cl2 HCl + S Example 4:

Fe + O2 Fe2O3 Classwork Assign oxidation numbers for each element. Then, for the following balanced redox reactions answer the following questions: 1) Fe(aq) + H2O2(aq) Fe+2(aq) + 2 OH-1(aq) a. Write all the oxidation numbers (identify what changes) b. Write the reactions on the lines _______________________ ________________________

(oxidation or reduction) (oxidation or reduction) c. Add the electrons to each reaction d. Identify each reaction as oxidation or reduction 2) Zn(s) + HCl(aq) H2(g) + ZnCl2(aq) 3) SbCl5 + 2 KI SbCl3 + I2 + 2 KCl