Chemistry 1 Chapter 22 &23 Oxidation Reduction Reactions The Students will be able to describe redox reactions and assign oxidation numbers to chemical compounds.

Oxidation Reduction Reactions Also called REDOX reactions Original, simple, definition of terms: Oxidation - combining with oxygen EX: CH 4 + 2O 2  CO 2 + 2H 2 O Reduction - loss of oxygen EX: 2H 2 O (l)  2H 2 (g) + O 2 (g) The Students will be able to describe redox reactions and assign oxidation numbers to chemical compounds.

Broader definition: Oxidation - atom or ion becoming more positive (losing electrons) in a chemical reaction. Reduction - atom or ion becoming less positive (gaining electrons) in a chemical reaction. The Students will be able to describe redox reactions and assign oxidation numbers to chemical compounds.

Oxidation IsIs Loss Reduction IsIs Gain LEO (Lose Electrons-Oxidation) the lion goes GER (Gain Electrons-Reduction) Use either pneumonic to remember which is Oxidation or Reduction. The Students will be able to describe redox reactions and assign oxidation numbers to chemical compounds.

Oxidation Numbers Oxidation Number - the real or apparent charge of an atom or ion. We will use these numbers to determine the loss or gain of electrons by different species of chemicals. The Students will be able to describe redox reactions and assign oxidation numbers to chemical compounds.

HERE’S THE RULES: 1 Free elements are assigned an oxidation state of zero. 2 The sum of the oxidation states of all atoms in a compound must equal the net charge of the compound. 3 The alkali metals (Li, Na, K, Rb, and Cs) in compounds are always assigned an oxidation state of Fluorine in compounds is always assigned an oxidation state of -1. The Students will be able to describe redox reactions and assign oxidation numbers to chemical compounds.

HERE’S THE RULES: 5 The alkaline earth metals (Be, Mg, Ca, Sr, Ba, and Ra) and also Zn and Cd in compounds are always assigned an oxidation state of Hydrogen in compounds is assigned an oxidation state of Oxygen in compounds is assigned an oxidation state of The Halogens (Cl, Br, I) in compounds are assigned an oxidation state of -1. The Students will be able to describe redox reactions and assign oxidation numbers to chemical compounds.

Rules for assigning oxidation numbers: 1. Ox. # of any elemental atom is zero. 2. Ox. # of any simple ion is the charge of the ion. 3. Ox. # for oxygen is -2 (except in peroxide, -1) 4. Ox. # for hydrogen is +1 (except in metal hydride, -1) 5. Sum of ox. #'s equals the charge on molecules or polyatomic ions. NaO2O2 Al Na + P 3- NaHLiH H2OH2O H2O2H2O (+1) + (-2) = 0 The Students will be able to describe redox reactions and assign oxidation numbers to chemical compounds.

EXAMPLE: Give the oxidation states of each element in the following molecules: O2O2 HCl +1 (+1) + (-1) = 0 0 Mn 2 O (x) + 3(-2) = 0 x = +3 The Students will be able to describe redox reactions and assign oxidation numbers to chemical compounds.

PO x + 4(-2) = -3 x = +5 MnO x + 2(-2) = 0 x = +4 SO x + 4(-2) = -2 x = +6 The Students will be able to describe redox reactions and assign oxidation numbers to chemical compounds.

HCO 3 - Zn(OH) x + 3(-2) = -1 x = +4 x + 2(-2) + 2(+1) = 0 x = +2 The Students will be able to describe redox reactions and assign oxidation numbers to chemical compounds.

Oxidation and Reduction always occur together. Both occur in a REDOX reaction. The Students will be able to describe redox reactions and assign oxidation numbers to chemical compounds.

EXAMPLE: Cu (s) + Ag + (aq)  Cu 2+ (aq) + Ag (s) Half Reaction - reaction that shows either oxidation or reduction. Cu (s)  Cu e- Ag e-  Ag (s) Reducing Agent - the substance that was oxidized. (Cu) Oxidizing agent - substance that was reduced. (Ag+) Cu loses e-, therefore it is oxidized Ag + gains e-, therefore it is reduced The Students will be able to describe redox reactions and assign oxidation numbers to chemical compounds.

REDOX Reaction Examples Identify the element oxidized, the element reduced, the oxidizing agent and the reducing agent for each of the following: MnO 2 + HCl  MnCl 2 + Cl 2 + H 2 O Mn Cl +4+2 Gained 2 e - Oxidized If it was Reduced, then the reactant that contains Mn acts as the “Oxidizing Agent”. (MnO 2 ) 0 Lost 1 e - Reduced If it was Oxidized, then the reactant that contains Cl acts as the “Reducing Agent”. (HCl) The Students will be able to describe redox reactions and assign oxidation numbers to chemical compounds.

Identify the element oxidized, the element reduced, the oxidizing agent and the reducing agent for each of the following: Cu + HNO 3  Cu(NO 3 ) 2 + NO 2 + H 2 O Cu N 0+2 Lost 2 e - Oxidized +5+4 Gained 1 e - Reduced If it was Reduced, then the reactant that contains N acts as the “Oxidizing Agent”. (HNO 3 ) If it was Oxidized, then the reactant that contains Cu acts as the “Reducing Agent”. (Cu) The Students will be able to describe redox reactions and assign oxidation numbers to chemical compounds.

Identify the element oxidized, the element reduced, the oxidizing agent and the reducing agent for each of the following: P + HNO 3 + H 2 O  NO + H 3 PO P N 0+5 Lost 5 e - Oxidized +5+2 Gained 3 e - Reduced If it was Oxidized, then the reactant that contains P acts as the “Reducing Agent”. (P) If it was Reduced, then the reactant that contains N acts as the “Oxidizing Agent”. (HNO 3 ) The Students will be able to describe redox reactions and assign oxidation numbers to chemical compounds.

Identify the element oxidized, the element reduced, the oxidizing agent and the reducing agent for each of the following: Bi(OH) 3 + Na 2 SnO 2  Bi + Na 2 SnO 3 + H 2 O Bi Sn +30 Gained 3 e - Reduced +2+4 Lost 2 e - Oxidized If it was Reduced, then the reactant that contains Bi acts as the “Oxidizing Agent”. (Bi(OH) 3 ) If it was Oxidized, then the reactant that contains Sr acts as the “Reducing Agent”. (Na 2 SrO 2 ) -2 The Students will be able to describe redox reactions and assign oxidation numbers to chemical compounds.

When iron is exposed to air, the iron oxidizes: Fe 0 → Fe e - The electrons released reduce the oxygen: O e - → O -2 Rust is a redox reaction!!! 4Fe + O 2 → 2Fe 2 O 3 The Students will be able to describe redox reactions and assign oxidation numbers to chemical compounds.

There’s no oxygen… How’s it rusting? The Students will be able to describe redox reactions and assign oxidation numbers to chemical compounds.

Bacteria facilitate the rust… SO Fe → Iron (?) oxide The Students will be able to describe redox reactions and assign oxidation numbers to chemical compounds.

Cu + O 2 → CuO CuO is a black color, but when mixed with acid from the atmosphere (acid rain), the compound forms a green coating called a patina. The Students will be able to describe redox reactions and assign oxidation numbers to chemical compounds.

Chemistry 1 Chapter 23 Electrochemistry The Students will be able to describe redox reactions and assign oxidation numbers to chemical compounds.

The interconversions of chemical and electrical energy are called ________________ ____________ all of which involve the transfer of ____________. This process occurs in a device called an _________________ _____________. ElectrochemicalCell Electrons Electrochemical Processes The Students will be able to describe redox reactions and assign oxidation numbers to chemical compounds.

We will utilize the activity series of metals on page 678 to determine reactivity in single replacement reactions. The simplified order from most reactive to least reactive: group I & II metals plus Al, the transition metals, H, "jewelry metals” (Cu, Hg, Ag, Au).

EXAMPLE: Circle the more reactive metal? Which one would be Oxidized? Reduced? (use the activity series) Fe / Cu Ca / Ag Au / H H / Na The other is Reduced Circled is Oxidized The Students will be able to describe redox reactions and assign oxidation numbers to chemical compounds.

EXAMPLE: Predict what will happen if an iron nail is dipped into a solution of CuSO 4. Write the balanced equation and the two half-reactions (reduction and oxidation reactions). Iron is above copper on the activity series, so the reaction does occur: Fe(s) + CuSO 4 (aq)  Oxidation: Reduction: FeSO 4 + Cu Fe  Fe e - Cu e -  Cu Fe [0  +2] Cu [+2  0] The Students will be able to describe redox reactions and assign oxidation numbers to chemical compounds.

Electrochemical cells that convert chemical energy into electrical energy are called _______ _____. The energy is produced by _____________ redox reactions. VoltaicCells Spontaneous The Students will be able to describe redox reactions and assign oxidation numbers to chemical compounds.

Voltaic cells can be separated into two ______ _____. A half cell consists of a metal rod or strip immersed in a solution of its ______. A salt bridge is a tube containing an ____________ solution. HalfCells Ions Electrolyte The Students will be able to describe redox reactions and assign oxidation numbers to chemical compounds.

Ions pass through the salt bridge to keep the charges balanced. _________ pass through an external wire. The metal rods in voltaic cells are called ______________. Oxidation occurs at the ________ and reduction occurs at the _____________. (An Ox and a Red Cat) The direction of electron flow is from the _________ to the __________. (FAT CAT ) Electrodes Anode Cathode AnodeCathode Electrons The Students will be able to describe redox reactions and assign oxidation numbers to chemical compounds.

Diagram of voltaic cell _________ Direction of electron flow ______________________ AnodeCathode Oxidation Reduction The Students will be able to describe redox reactions and assign oxidation numbers to chemical compounds.

____ _____ : a voltaic cell in which the electrolyte is a paste. Example: a flashlight battery. DryCell The Students will be able to describe redox reactions and assign oxidation numbers to chemical compounds.

 The inexpensive dry cell batteries consist of a _______ container that acts as the ________, a __________ rod that acts as the _________ and an electrolyte paste of MnO 2, ZnCl 2, NH 4 Cl and H 2 O.  The pH of this solution is acidic and tends to corrode the zinc case. An alkali battery has the NH 4 Cl replaced with KOH and is basic instead of ________. This makes the battery last longer. Zinc Anode Cathode Graphite Acidic The Students will be able to describe redox reactions and assign oxidation numbers to chemical compounds.

5 to 10 times the energy of a common dry cell. The following reaction represents the REDOX reaction taking place within the battery: Zn (s) + 2MnO 2 (s) + H 2 O (l)  Zn(OH) 2 (s) + Mn 2 O 3 (s) The Students will be able to describe redox reactions and assign oxidation numbers to chemical compounds.

A group of cells connected together make up a ____________. A lead storage battery is commonly used in a ________. In this type of battery the anode is ___________. The cathode is _________________. The electrolyte (battery acid) is ____________. Battery Car Lead Lead (IV) Oxide H 2 SO 4 The Students will be able to describe redox reactions and assign oxidation numbers to chemical compounds.

Below is the reaction that occurs during discharge of the battery. PbO 2 + Pb + 2H 2 SO 4  PbSO 4 + 2H 2 O + ENERGY The Students will be able to describe redox reactions and assign oxidation numbers to chemical compounds.

Define fuel cell: What are some uses for fuel cells? The process of forcing a current through a cell to produce a chemical change is ____________. An electrolytic cell is used to change ______________ into __________________. Electrolysis Voltaic cell in which the fuel is oxidized and electrical energy is obtained continuously. SubmarinesSpace ShuttleMilitary Vehicles ElectricalChemical Energy The Students will be able to describe redox reactions and assign oxidation numbers to chemical compounds.

Corrosion - Rusting of Fe is a good example. When H 2 O and O 2 are present, Fe is oxidized to Fe(OH) 3 and Fe 2 O 3. Both of which are components of rust. The chemical or electrochemical reaction between a material, usually a metal, and its environment that produces a deterioration of the material The Students will be able to describe redox reactions and assign oxidation numbers to chemical compounds.

Sacrificial metal - EX: Galvanized steel - iron coated with Zn. The more active metal, in this case Zn, corrodes first and leaves behind a protective oxide that prevents moisture or oxygen from corroding the iron. a more reactive metal used to protect a less reactive metal from corrosion The Students will be able to describe redox reactions and assign oxidation numbers to chemical compounds.

Why purchase a “galvanized trailer” instead of one that is painted? The Students will be able to describe redox reactions and assign oxidation numbers to chemical compounds.

Lithium Ion Batteries Used in: Lap-Top Computers Cell Phones iPods / mp3 Players The Students will be able to describe redox reactions and assign oxidation numbers to chemical compounds.

Metallic lithium anode or lithium alloy anode, which provides a negative charge. Oxidized – loses electrons A high surface area carbon cathode, which provides a positive charge. Reduced – gains electrons The Students will be able to describe redox reactions and assign oxidation numbers to chemical compounds.