U4 S2 L5STSE

Textbook Readingspages 764-766: Disposable Batteries pages 787-788: Rechargeable Batteries pages 802-803: Automobile Engines Pages 796: Industrial extraction and refining of metalsPages 798 – 801 Issues involving elecxtrochem.

Textbook Practice Itemspage 789: items 4 and 5 page 803: items 29, 30, 31 and 32

Upon completion of this lesson, you should be able to:

• define primary battery, secondary battery and identify common examples of each including dry cell, alkaline, button, lead storage, and Ni-Cd

• compare the efficiency of burning hydrogen in a fuel cell with burning it in a combustion reaction

• Batteries are galvanic cells (electrochemical cells).– They consist of two or more half-cells connected in series with two terminals. – One terminal is positive (+) while the other is negative (-). – Electrons build up at the negative terminal of the battery and flow to the positive

terminal when a circuit is completed. – Typically, a circuit includes a load - something that uses the electricity like a light

bulb or a motor.

• Two types of batteries:– primary or disposable batteries p764

• cannot be recharged. It stops working when either the reducing agent or the oxidizing agent is completely consumed.

• Button batteries, AAA, AA, C, D ….• Dry cells (cheap ones) , Akaline batteries – duracell, energizer, Lithium …

– secondary or rechargeable batteries. p787• Ni/Cd rechargables• Car batteries – lead storage battery (lead acid battery)

Fuel Cells• A fuel cell is sometimes called a flow battery

2(g) (aq) 2 (l)

2(g) 2

2(g) 2(g) 2

aq)

)

(

(l

H 2OH 2H O 2e

O 2H O 4e 4OH

2H O 2H O

ANODE CATHODE

LOAD

Pollution FreeElectrolysis ofwater to makeH2 and O2

p 802

Corrosion p 798• From hot water tanks to outboard motors to battle

ships …. corrosion is a major concern!• Sacrificial anode rods (oxidized metal)

– Usually a piece of Zn or Mg metal. Why?• Most reactive metals (lowest on the standard reduction

table)• The metal will protect all other metals above it on the

table. In other words the lower the metal the more reactive (easier to oxidize and acts as the anode)

Cathodic protection:A DC current is passed through the object you wish to protect from oxidizing. The tank in this case is reduced – gaining mass!

Creates a DC current from AC

Mining to metallurgy STSE reading / p 796Metallurgy is the science of extracting and refining metals from ores and the

compounding of metals to form alloys • Native metals - occur in nature as pure metals• Mineral – a naturally occurring substance that has a defined chemical

composition.• An ore is a rock that contains commercially viable amounts of minerals.

Metals and Minerals Formulas and Names

Native Metals Ag, Au, Bi, Cu, Ir, Os, Pd, Pt

Carbonate MineralsCaCO3 (calcite), CaCO3●MgCO3 (dolomite), FeCO3 (siderite), BaCO3 (witherite)

Halide Minerals CaF2 (fluorite), NaCl (halite)

Oxide MineralsAl2O3●2H2O (bauxite), Cu2O (cuprite), Fe2O3 (haematite), Fe3O4 (magnetite)

Sulfide MineralsCu2S (chalcocite), CuFeS2 (chalcopyrite), NiS (millerite), Fe9Ni9S16 (pentlandite), FeS2 (pyrite)

Three main steps in obtaining a pure metal from its ore.1. Primary treatment

• Primary treatment is the process that concentrates the mineral. • It is conducted at the mine site. (crushing, froth flotation)

2. Extracting the metal • Extraction involves either pyrometallurgy or hydrometallurgy.

• Pyrometallurgy (or pyromet for short) involves heating an ore in a blast furnace at temperatures above 1500°C to convert the ore to a form that can be refined.

Adv: Efficient, inexpensive - proven technology, readily availableDisadv: pollution(CO2 - greenhouse gas, SO3 -acid rain!, not 100 % pure product

• Hydrometallurgy (or hydromet, for short) involves the use of aqueous chemicals and much lower temperatures to separate the metal from its ore. (Leaching: in situ, heap, vat)

Issues: potentially hazardous chemicals used in leaching.Adv: fewer impurities, less pollution, sulfuric acid by product is marketable

3. Refining the metal • Electrowinning – reduction of the dissolved metal ions by an inert anode.• Electrorefining involves removing impurities in which the anode of the impure

metal is oxidized and then the pure ions produced are reduced on a cathode.Issues: rerquires large amount of electricity – sources questionable!

The refining of nickel is accomplished in one of two ways. 1. Pyromet extraction (roasting)

The Extracted Nickel sulfide can be refined in one of two ways:1. Mond Process: converting Ni3S2 to NiO which is refined into pure nickel by

distillation (heat). Still may need to be electrorefined to remove impurities.2. Electrolysis (Electrowinning): reducing the nickel in Ni3S2 in an electrolytic cell.

• This is known as electrowinning. At the anode of the electrolytic cell, the Ni3S2 reacts to produce Ni2+ ions and S8.

• Ni2+ is then reduced at the cathode to produce nickel metal.

2. Hydromet extraction (dissolving)• Extraction by leaching of the ore to produce a solution that contains Ni ions.

(in situ, heap, vat leaching)• The Ni ions are then reduced to Ni metal electrolysis (electrowinning) with an

inert anode.