Making Use Of Metals.pptx

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This is a chunk of rock salt, the ore for sodium(NaCl)

This is a piece of bauxite, the ore for aluminum (Al2O3)

FIRST METHOD (USING CARBON MONOXIDE)

1) Roast zinc sulfide in air and the products are zinc oxide and sulfur dioxide Equation : 2ZnS + CO > Zn + CO2 2) React the zinc oxide with carbon monoxide to obtain zinc and carbon dioxide

Equation: ZnO + CO > Zn + CO2 The final product contains a slag of impurities that can be separated by fractional distillation

SECOND METHOD ( USING ELĒCTROLYSIS )

1) Dissolve zinc oxide in dilute sulfuric acid (H2SO4) 2) Zinc oxide neutralizes the acid giving a solution of zinc sulfate ( ZnSO4 ) 3) Zinc is deposited at the cathode after electrolysis Half equation: Zn2+ + 2ē > Zn

Reactions, products and waste gases

Comments

Stage 1: The coke burns, giving off heat The blast if hot air starts the coke burning. It reacts with the oxygen to give carbon dioxide C + O2 > CO2

- It is a redox reaction - It is an exothermic reaction, heat is given off

Stage 2 : Carbon monoxide is made The carbon dioxide reacts with more coke CO2 + C > CO

- Carbon dioxide is reduced to carbon monoxide. - It is an endothermic reaction , heat is absorbed

Stage 3 : The iron (lll) oxide is reduced Carbon monoxide reacts with the iron ore giving liquid iron. Fe2O3 + 3CO > 2Fe +3CO2

- Carbon monoxide is itself oxidized to carbon dioxide

What is limestone for? Limestone breaks down in the heat of the furnace CaCO3 > CaO + CO2 Calcium oxide reacts with silicon dioxide to form a slag calcium silicate, that is skimmed off CaO + SiO2 > CaSiO3

- Molten slag is drained off. It turns into a solid when cooled

THE REACTIONS AT THE ELECTRODES Once alumina dissolves, Al2O3 ions are free to move At the cathode : aluminum ions gain electrons 4Al3+ +12ē >4Al Pure aluminum drops to the bottom and run off at intervals At the anode : oxygen ions lose electrons 6O2- > 3O2 + 12ē Carbon is oxidized at the anode C + O2 > CO2 Overall reaction 2Al2O3 > 4Al + 3O2

What is an alloy ? An alloy is a metal made by combining two or more metallic elements

EXAMPLES

Alloy

Made from

Special properties

Uses

Brass

70% copper 30% zinc

Harder than copper and does not corrode

Musical instruments and ornaments

Aluminum alloy 7075 TF

90.25% aluminum 6% zinc 2.5% magnesium 1.25% copper

Light and strong and Aircraft also does not corrode

Alloys

Made from

Special properties

Uses

Mild steel

99.5% iron 0.3% carbon

Hard and strong

Buildings, car body, machinery,ships

Stainless steel

70% iron 20% chromium 10% nickel

Hard and rustproof

Cutlery and chemical equipments

BASIC OXYGEN CONVERTER Removal of impurities The oxygen reacts with carbon and sulfur to give off gases carbon dioxide and sulfur dioxide. The oxygen then reacts with phosphorus to give phosphorus (V) oxide, a solid. Calcium oxide is then added, it reacts with phosphorus(V) oxide and silicon dioxide to give a slag which can be skimmed of.