Metals extraction Chapter 15 Hana Huzien Introduction • The Earth’s crust contains metals such as gold and metal compounds such as iron oxide and aluminum oxide in the rocks. • A rock from which a metal can be extracted is called an ore. • An ORE is a rock containing enough of a metal compound to extract the metal economically. • Most ores are oxides or sulfides. • Important ores: • Hematite: iron ore • Bauxite: aluminum ore • Zinc blende: zinc ore Aluminum is the most abundant common metal in the earth’s crust The Reactivity Series of Metals Very reactive Fairly reactive Not very reactive Not at all reactive POTASSIUM K SODIUM Na CALCIUM Ca MAGNESIUM Mg ALUMINIUM Al (CARBON) ZINC Zn IRON Fe LEAD Pb (HYDROGEN) COPPER Cu SILVER Ag GOLD Au PLATINUM Pt The Reactivity Series of Metals Very reactive Fairly reactive Not very reactive Not at all reactive POTASSIUM K SODIUM Na CALCIUM Ca MAGNESIUM Mg ALUMINIUM Al (CARBON) ZINC Zn IRON Fe LEAD Pb (HYDROGEN) COPPER Cu SILVER Ag GOLD Au PLATINUM Pt Metals above carbon must be extracted from their ores by electrolysis of their molten compounds The Reactivity Series of Metals Very reactive Fairly reactive Not very reactive Not at all reactive POTASSIUM K SODIUM Na CALCIUM Ca MAGNESIUM Mg ALUMINIUM Al (CARBON) ZINC Zn IRON Fe LEAD Pb (HYDROGEN) COPPER Cu SILVER Ag GOLD Au PLATINUM Pt Metals above carbon must be extracted from their ores by electrolysis Metals below carbon can be extracted from their ores using reduction with coke or charcoal The Reactivity Series of Metals Very reactive Fairly reactive Not very reactive Not at all reactive POTASSIUM K Metals above carbon must be SODIUM Na extracted from their ores by CALCIUM Ca is a chemical electrolysis MAGNESIUM Mg reaction ALUMINIUM Al in which oxygen is (CARBON) removed from a compound. ZINC Zn Metals below carbon can be extracted from IRON Fe their ores using reduction with coke or charcoal LEAD Pb (HYDROGEN) COPPER Cu SILVER Ag GOLD Au PLATINUM Pt REDUCTION The Reactivity Series of Metals Very reactive Fairly reactive Not very reactive Not at all reactive POTASSIUM K SODIUM Na CALCIUM Ca MAGNESIUM Mg ALUMINIUM Al (CARBON) ZINC Zn IRON Fe LEAD Pb (HYDROGEN) COPPER Cu SILVER Ag GOLD Au PLATINUM Pt Metals above carbon must be extracted from their ores by electrolysis Metals below carbon can be extracted from their ores using reduction with coke or charcoal Metals below hydrogen don’t react with water or acid. They don’t easily tarnish or corrode. The Reactivity Series of Metals Very reactive Fairly reactive Not very reactive Not at all reactive POTASSIUM K SODIUM Na CALCIUM Ca MAGNESIUM Mg ALUMINIUM Al (CARBON) ZINC Zn IRON Fe LEAD Pb (HYDROGEN) COPPER Cu SILVER Ag GOLD Au PLATINUM Pt Metals above carbon must be extracted from their ores by electrolysis Metals below carbon can be extracted from their ores using reduction with coke or charcoal Metals below hydrogen don’t react with water or acid. They don’t easily tarnish or corrode. The Reactivity Series of Metals Very reactive Fairly reactive Not very reactive Not at all reactive POTASSIUM K SODIUM Na CALCIUM Ca MAGNESIUM Mg ALUMINIUM Al (CARBON) ZINC Zn IRON Fe LEAD Pb (HYDROGEN) COPPER Cu SILVER Ag GOLD Au PLATINUM Pt Metals above carbon must be extracted from their ores by electrolysis Metals below carbon can be extracted from their ores using reduction with coke or charcoal Metals below hydrogen don’t react with water or acid. They don’t easily tarnish or corrode. Metal extraction and reactivity series Iron extraction What do you need to learn? • describe the extraction of iron from iron ore in the blast furnace, • explain the role of limestone and coke in the process, https://youtu.be/g3hQpb8ES6c coke Iron ore Reactants Furnace Hot air blast Limestone coke Iron ore Limestone Purified coal Hematite Calcium carbonate Reactants Crushed Furnace Hot air blast Crushed coke Iron ore Limestone Reactants Furnace Hot air blast Products Molten iron Molten slag Step 1 Step 2 Step 3 The blast furnace • What do you need to know?? • You should be able to recognize a diagram of furnace for iron extraction. • You must be able to label a diagram. • Know the key reactions of the furnace. • First of all, what is a blast furnace? • A furnace is an enclosed chamber in which heat is produced. • Blast is a mass of air that moves very quickly and forcefully. • In the blast furnace a strong current of hot air is blown in at the bottom of the furnace. • The temperature of the hot air is between 550⁰C and 850 ⁰C. this high enough to react with coke. Extracting iron ….. Summary • The main ore of iron is hematite. It contains 60% iron. • Hematite is largely iron(III) oxide. • We extract iron by reduction of iron(III) oxide with carbon. • The main reducing agent is carbon monoxide, but in some parts of the blast furnace carbon also reduces the iron(III) oxide. Extracting iron ….. Summary • The raw materials used in the extraction of iron are: 1. Hematite: Fe2O3 2. Air: oxygen. 3. Limestone: CaCO3 (calcium carbonate) • Coke: this is coal (carbon) from which some impurities have been removed. (it is not a raw material because it has been treated by heating) • The main process in the blast furnace of iron extraction is: 1. Reduction (reaction with carbon/carbon monoxide). Steps for iron extraction 1. A blast of air is blown into the bottom of the furnace. The coke burns in the hot air blast to form carbon dioxide: C (s) + O2 (g) CO2 (g) (this process produces heat in the furnace) 2. Carbon dioxide goes up and reacts with excess coke to form carbon monoxide: CO2 (g) C (s) + 2CO (g) 3. The carbon monoxide reduces the iron(III) oxide to iron (most of the iron is produced in this way): Fe2O3 (s) + 3CO (g) 2Fe (l) + 3CO2 (g) • In the hotter parts of the furnace, carbon may reduces iron(III) oxide directly: Fe2O3 (s) + 3C (s) 2Fe (l) + 3CO (g) Why do we add limestone? • Hematite contains sand (silicon(IV) oxide) as a major impurity. Limestone helps remove most of the impurities. 1. The heat from the furnace decomposes the limestone: CaCO3 (s) heat CaO (s) + CO2 (g) • The calcium oxide reacts with the silicon(IV) oxide to form a ‘slag’ of calcium silicate: CaO (s) + SiO2 (s) CaSiO3 (l) Note: you have to be able to write a word and symbol equations for all the reactions in the blast furnaces. Important notes ….. • The iron produced flows down to the bottom of the furnace, and is removed from time to time as a liquid. It flows into moulds and is left to solidify. • The hot waste gases exiting from the top of the furnace are used to heat the air going into the furnace thus reducing the energy costs. • The liquid slag runs down the furnace and forms a layer on top of the liquid iron because it is less dense than liquid iron. • The solid slag is used as a building material, particularly in road building. Q.1 Q.2
