10: Occurrence and Extraction of Metals Flashcards
What is the most abundant element by mass in the Earth’s crust?
Oxygen (49.2%)
What is the most abundant metal by mass in the Earth’s crust?
Aluminium (7.5%)
What are ores?
Ores are rocks containing minerals in concentrations that are high enough for economical extraction.
Name 2 oxide ores and the names of metal compounds found in these ores.
Bauxite: hydrated aluminium oxide Haematite: iron(III) oxide
What is the chemical formula of hydrated aluminium oxide?
Al2O3·2H2O
What is the chemical formula of iron(III) oxide?
Fe2O3
Name 4 sulphide ores and the names of metal compounds found in these ores.
Copper pyrite: copper(II) iron(II) sulphide
Cinnabar: mercury(II) sulphide
Galena: lead(II) sulphide
Zinc blende: zinc sulphide
What is the chemical formula of copper pyrite?
CuFeS2
What is the chemical formula of mercury(II) sulphide?
HgS
What is the chemical formula of lead(II) sulphide?
PbS
What is the chemical formula of zinc sulphide?
ZnS
Name three carbonate ores and the names of metal compounds found in these ores.
Calamine: zinc carbonate
Magnesite: magnesium carbonate
Malachite: copper(II) carbonate
What is the chemical formula of zinc carbonate?
ZnCO3
What is the chemical formula of magnesium carbonate?
MgCO3
Name one halide ore and the metal compound found inside.
Rock salt: sodium chloride
What is roasting and which type of metal compound is it applicable to?
Roasting refers to the process of heating the concentrated ore strongly in the presence of excess air. It is commonly used for sulphide ores to convert them into oxide ores.
What is calcination and which type of metal compound is it applicable to?
Calcination refers to the process of heating the concentrated ore strongly in the without / with a limited supply of air. It is commonly used for carbonate ores to convert them into oxide ores.
List three methods metals can be extracted from their oxides.
by heating alone, by (carbon / carbon monoxide) reduction, by electrolysis
Which additional substance is used in the extraction of aluminium and why?
Cryolite is added to lower the melting point of aluminium as lower operation costs are needed for less heat energy.
Why does bauxite have to be molten in order for electrolysis to take place?
Since the ore must be molten for ions to move freely, the ore must be heated to melt.
List three reasons why the material of the electrode used in extraction of aluminium is chosen.
The material is graphite.
1. It conducts electricity.
2. It has a high melting and boiling point.
3. It is chemically inert.
Do electrodes involved in the extraction of aluminium need to be replaced regularly?
The positive electrode does. This is because at the positive electrode, oxygen ions are attracted and form oxygen atoms, which oxidises carbon in high temperature to become carbon dioxide.
Can carbon electrodes be made of diamond instead?
No, because diamond has a giant covalent structure in which no delocalised electrons can be found, so it cannot conduct electricity.
Why do aluminium ions and oxygen ions break the octet rule to form aluminium atoms and oxygen atoms in electrolysis?
The presence of electrical energy forces the ions to break the octet rule.
What is the name of the equipment used to extract iron industrially?
Blast furnace
What materials are added to the blast furnace for the extraction of iron?
- iron ore, such as haematite, containing iron(III) oxide
- coke (carbon)
- limestone, which is used to purify the iron.
How is iron extracted industrially?
- Hot air is shot at the bottom of the furnace.
- Coke (carbon) reacts with hot oxygen to form carbon dioxide.
- Carbon dioxide rises and reacts with hot carbon to form carbon monoxide.
- Carbon monoxide reduces iron(III) oxide back to iron. (carbon monoxide + iron(III) oxide -> iron + carbon dioxide)
- The high temperature decomposes calcium carbonate to calcium oxide and carbon dioxide.
- Calcium oxide reacts with impurities (silicon dioxide) to form calcium silicate, which runs down to form the slag.
Is the year of discovery of the metals related to the abundance of the metals?
No, it is related to the reactivity, since higher technology is required to extract more reactive metals.
How does recycling aluminium help save energy?
Aluminium is extracted from molten aluminium oxide at high temperatures by electrolysis. The process requires huge amounts of electrical energy. Therefore, recycling saves energy, since recycling aluminium does not involve electrolysis.
