Case: Metals are extracted from their ores through various methods depending on the reactivity of the metal. Highly reactive metals like sodium and calcium are extracted by electrolysis of their molten salts. Moderate metals like zinc, iron, and copper are extracted using chemical reduction processes.
For example, in the extraction of zinc, zinc oxide (ZnO) is first reduced to zinc metal by carbon. The reduction of iron from its ore, hematite (Fe₂O₃), is done through a blast furnace, where carbon monoxide reduces iron oxide to iron metal.
Questions:
Which of the following methods is used for the extraction of zinc from its ore, zinc oxide?
The extraction of iron from its ore hematite involves:
Which of the following ores of iron is commonly used in the extraction of iron in a blast furnace?
In the extraction of metals, the method of electrolysis is used for metals that are:
Case: Roasting and calcination are two important processes used in the extraction of metals from their ores. Roasting involves heating an ore in the presence of excess oxygen, which results in the conversion of metal sulfides to oxides. For instance, zinc sulfide (ZnS) is roasted to form zinc oxide (ZnO).
On the other hand, calcination involves heating the ore in the absence of oxygen, often in a rotary kiln. It is used to remove volatile components like water or carbon dioxide from ores. For example, limestone (CaCO₃) is calcined to form calcium oxide (CaO) and carbon dioxide.
Questions:
Which process involves heating an ore in the presence of oxygen to form an oxide?
Calcination is used for which of the following processes?
In the roasting of zinc sulfide (ZnS), the product formed is:
The calcination of limestone (CaCO₃) produces:
Case: Leaching is a process by which metals are extracted from their ores using chemical reagents. It is commonly used for ores that are either too low in metal content or too difficult to reduce by traditional methods. For example, bauxite, the primary ore of aluminum, is treated with NaOH in a process known as the Bayer Process to extract aluminum hydroxide.
Similarly, in the extraction of gold, cyanide is used to form a soluble complex with gold, allowing it to be separated from the ore.
Questions:
The Bayer process is used to extract:
In the extraction of gold using cyanide, the metal is converted into:
Leaching of bauxite with NaOH results in the formation of:
Which of the following reagents is used in the extraction of gold from its ore?
Case: Aluminum is a highly reactive metal and is extracted using the Hall-Héroult process, which involves the electrolysis of alumina (Al₂O₃) dissolved in molten cryolite (Na₃AlF₆). During electrolysis, aluminum metal is deposited at the cathode, and oxygen gas is released at the anode. This process is highly energy-intensive but is essential for obtaining aluminum from its oxide.
Aluminum metal is used extensively in industry due to its lightweight, corrosion-resistant properties and is widely employed in packaging, transportation, and construction.
Questions:
The Hall-Héroult process is used for the extraction of:
In the Hall-Héroult process, aluminum is obtained at the:
The electrolyte used in the Hall-Héroult process is:
In the electrolysis of alumina, oxygen is released at the:
Case: The reduction of metal oxides is a critical step in the extraction of many metals. The method of reduction depends on the reactivity of the metal. Metals like gold and platinum are found in their native state and do not require reduction. However, metals like iron, copper, and zinc are found as oxides and must be reduced.
For example, copper oxide (CuO) can be reduced by heating with hydrogen gas to form copper metal. Similarly, zinc oxide can be reduced by heating with carbon to yield zinc metal.
Questions:
The reduction of copper oxide (CuO) to copper is carried out by:
Zinc oxide is reduced to zinc by heating with:
Gold and platinum are generally found in nature as:
The process of reduction involves: