Metals and Metallurgy - SS2 Chemistry Past Questions and Answers - page 1
Which of the following is NOT a commonly used method for the extraction of metals?
Smelting
Electrolysis
Distillation
Leaching
Which of the following statements about smelting is true?
Smelting involves the use of heat to extract metals from their ores.
Smelting uses chemical solvents to dissolve metals from their ores.
Smelting relies on the application of electrical currents to extract metals.
Smelting is primarily used for the purification of metals.
What is the primary purpose of leaching in the extraction of metals?
To dissolve impurities from the ore.
To convert the metal oxides into a more reactive form.
To separate the metal from the ore using magnetic fields.
To remove the metal from the ore using high-pressure steam.
Which of the following methods is commonly used to refine copper metal?
Electrolysis
Distillation
Smelting
Leaching
Which of the following metals is typically extracted through the process of electrolysis?
Aluminium
Iron
Gold
Silver
Which of the following techniques is used for the concentration of ores?
Leaching
Electrolysis
Froth flotation
Smelting
Which of the following statements about the Bessemer process is true?
It is a method for the extraction of iron from its ore.
It is a process used for refining precious metals.
It is a method for the extraction of aluminium from its ore.
It is a process used for refining copper.
Which of the following metals is extracted using the cyanide process?
Gold
Copper
Iron
Aluminium
Describe the process of extraction of metals from their ores. Discuss the principles and techniques involved in the extraction process. Provide examples.
The extraction of metals from their ores involves several principles and techniques to separate the desired metal from the ore matrix. The process typically includes the following steps:
a. Mining: The first step is to obtain the ore from the Earth's crust through mining. Ores are rocks or minerals that contain a high enough concentration of the desired metal.
b. Crushing and Grinding: The mined ore is crushed into smaller pieces and then ground into a fine powder. This increases the surface area of the ore, facilitating subsequent chemical reactions.
c. Concentration: The ore is concentrated to remove impurities and increase the metal content. Techniques such as froth flotation, magnetic separation, or gravity separation are used to separate the ore particles based on their physical or chemical properties.
d. Roasting or Calcination: Some ores require roasting or calcination, which involves heating the ore in the presence of air. This step helps in the removal of volatile impurities, moisture, and other unwanted substances.
e. Reduction: The reduced metal is obtained by applying various reduction techniques. Common methods include smelting, where the ore is heated with a reducing agent (such as carbon) to remove oxygen and obtain the metal in a more pure form.
Examples of extraction processes include the extraction of iron from its ore (hematite) using the blast furnace method and the extraction of aluminium from bauxite through the Bayer process and electrolysis.
Discuss the importance of refining metals after extraction. Explain the techniques used in the refining process. Provide examples.
Refining of metals is crucial after extraction to purify the metal and remove impurities that may affect its properties and applications. The refining process involves the following techniques:
a. Smelting: Smelting is often the first step in the refining process, where the extracted metal is heated with suitable fluxes or other chemicals to remove impurities through chemical reactions or volatilization.
b. Electrolysis: Electrolysis is widely used for refining metals that are highly reactive or have high melting points. In this process, an electric current is passed through an electrolyte containing a dissolved metal compound. The metal ions are reduced at the cathode, while impurities settle as anode mud or are removed by selective anode dissolution.
c. Distillation: Distillation is employed for refining metals with high vapour pressures, such as zinc and mercury. The metal is heated to its boiling point, and the vapours are collected and condensed to obtain pure metal.
d. Zone Refining: Zone refining is a technique used for obtaining ultra-pure metals, such as silicon and germanium. A molten zone is passed through a rod of impure metal, causing impurities to move along with the zone. This process is repeated several times to concentrate impurities at one end, leaving behind a highly pure metal.
For example, copper is refined through electrolysis, where impure copper is used as the anode and pure copper as the cathode. During electrolysis, copper ions from the anode are reduced at the cathode, resulting in the deposition of pure copper. Overall, refining processes ensure that the extracted metals meet the required purity standards and have the desired properties for various industrial applications.