Why Is Extraction of Crude Metal Important in Chemistry?
Learn the Extraction of Crude Metal from Concentrated Ore
The discovery of metals and its various innovative uses have paved the way to the modern civilization we are currently living in. Almost everything we use in our daily lives is made of metal. From medical equipment to agricultural infrastructure, clothing manufacturing to residential constructions, you will find different types of metals used for various purposes. This is why metallurgy has been added as a part of the chemistry syllabus in the advanced classes. Learning how to extract metals from ores using the inorganic properties of the constituents is very important.
The concept page of Vedantu has been prepared by the top mentors so that students can understand these topics properly. On this concept page, students will learn how the extraction of crude metal from concentrated ore is done in different ways. Follow how the experts have used the simplest language to make these concepts easy to understand for students. Find out the best ways to tackle your queries by using this concept page as a reference.
What is the Extraction of Metals?
Every ore is extracted from the mines with the sole purpose of collecting a particular metal. The ore is mined and then sent to the refining chambers. There are several processes involved in concentrating the ore of a metal. This concentrating part starts with pulverization of the big ore chunks in the jaw crushes or ball mills.
After completely reducing the grain size of the ore, it is then sent to the concentrating segment where the amount of ore containing the metal is increased by removing impurities as much as possible. The processes involved in this part of the metal extraction process are:
Hydrolytic Method
Water is sprayed with a force on the pulverized ore grains. The metal-containing grains settle down on the grooved inclined table and the impurities wash down.
Magnetic Separation
This is one of the easier metal ore concentration processes used for ferromagnetic substances. The wheels running a conveyor belt are magnetic. They keep the magnetic ore particles stuck to the belt and the rest of the impurities fall down.
Froth Floatation
This is a process of concentrating the ore where a dual medium of oil and water is used. Compressed air is sent in the mixture to form frothing in the oil medium. The ore particles containing the metal form froths that are collected on the top of the oil medium. The impurities that are unable to get dissolved either in oil or water settle down.
After these processes, the concentrated ore is then subjected to another purification method. This is where the metal is then separated from the ore by means of heating. It is either done in the presence or absence of air. To remove it from the concentrated ore, the original state has to be converted into an oxide first. This is done by following the two processes related to the extraction of crude metal from concentrated ore mentioned below.
Calcination
This is a process where the concentrated ore is subjected to immense heat in a very limited supply of air or oxygen. It is sometimes done in the absence of oxygen. The hydrated oxides lose all the water molecules associated leaving the oxide of the metal behind. In fact, it is also done to break down the carbonated salts of different elements. For instance, it is done to remove the associated water molecules of ferric oxide. It is also used to break and remove the carbonate functional group from the salts of calcium and magnesium. When you will study this process of extraction of crude metal from the ore with the help of examples on this concept page, it will become a lot easier to understand.
Roasting
Roasting, on the other hand, is heating the concentrated ore to extreme temperature in the presence of oxygen so that the sulphides of the ores can be oxidized to form metal oxides. The superheated oxygen in the air removes the sulphide group in the metal ore in the form of sulphur oxides and leaves the oxide of metals behind. This extraction of crude metal from the ore is done for extracting copper from copper sulphides, lead from lead sulphides and zinc from zinc sulphides.
After this step, the oxide of the metals is then reduced by heating them in the presence of carbon. Carbon reduces the oxides to pure metals as it takes away oxygen to form carbon oxides.
FAQs on Extraction of Crude Metal from Concentrated Ore: Key Steps
1. What is the main purpose of extracting a crude metal from its concentrated ore?
The main purpose is to convert the metal compound found in the ore (like an oxide or sulphide) into its basic, elemental form. This process is chemically known as a reduction, where the metal ion gains electrons to become a neutral metal atom. The result is an impure or 'crude' metal, which is then purified later.
2. What are the two main steps to get crude metal from a concentrated ore?
The extraction from a concentrated ore generally involves two key stages:
- Conversion to Oxide: The concentrated ore is converted into its metal oxide form, as oxides are usually easier to reduce. This is done through processes like roasting (heating in the presence of air) or calcination (heating in the absence of air).
- Reduction of the Oxide: The metal oxide is then heated with a suitable reducing agent (like carbon) or processed through electrolysis to remove the oxygen, leaving behind the crude metal.
3. Why isn't there one single method to extract all metals from their ores?
A single method doesn't work because different metals have different chemical properties, mainly their reactivity. The choice of extraction method depends on the metal's position in the reactivity series:
- High-reactivity metals (like sodium, aluminium) are very stable and require a powerful method like electrolysis.
- Medium-reactivity metals (like iron, zinc) can be extracted using chemical reduction with carbon in a process called smelting.
- Low-reactivity metals (like copper, mercury) can often be extracted simply by heating their ores in air.
4. What is smelting, and when is it used in metal extraction?
Smelting is a common extraction method where a metal oxide is heated to a high temperature with a reducing agent, typically carbon (in the form of coke). It is primarily used for moderately reactive metals like iron, zinc, and lead. A substance called a flux is also added to remove impurities as a molten slag.
5. What is the difference between calcination and roasting?
Both are processes used to convert ores into metal oxides, but they differ based on the presence of air. Calcination is the process of heating an ore strongly in the absence of air, typically used for carbonate ores (like ZnCO₃). Roasting involves heating an ore in the presence of excess air, which is necessary for sulphide ores (like ZnS).
6. Why is the metal obtained from extraction called 'crude metal' and not pure metal?
It is called 'crude metal' because the extraction process itself leaves behind several impurities. These can include unreacted reducing agents (like carbon), other metals present in the original ore, and non-metallic elements like silicon or phosphorus. This impure metal must undergo a final step called refining to achieve the desired level of purity for use.
7. Can you give a real-world example of extracting a common metal?
A classic example is the extraction of iron from its ore, haematite (Fe₂O₃), in a blast furnace. The concentrated ore is heated with coke (carbon) as the reducing agent and limestone (calcium carbonate) as the flux. The carbon reduces the iron oxide to molten, crude iron, while the limestone removes sandy impurities, forming slag. The crude iron produced is known as pig iron.
8. Why is it important to concentrate an ore before trying to extract the metal from it?
Concentrating an ore is a crucial first step because it removes most of the worthless rocky and earthy impurities, known as gangue. Extracting metal without this step would be highly inefficient and expensive, as a large amount of energy and chemicals would be wasted on processing materials that contain no valuable metal.
