Metallurgy Quiz - ICSE Class 10 Chemistry
Free practice quiz: Metallurgy (ICSE Class 10 Chemistry). 45 multiple-choice questions with answers and explanations. Play online, no sign-up needed.
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Which of the following processes is NOT used for the extraction of highly electropositive metals like sodium?
- Electrolytic reduction of fused salts
- Thermal decomposition of their oxides
- Electrolysis of molten chlorides
- Electrolysis of aqueous solutions
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Answer: D. Electrolysis of aqueous solutions
Highly electropositive metals like sodium cannot be extracted by electrolysis of their aqueous solutions because water itself is more easily reduced than the metal ions. Electrolysis of fused salts or molten chlorides, or thermal decomposition of their oxides (in certain cases, though less common for sodium), are preferred methods.
Which of the following is NOT an example of amphoteric oxide, which can react with both acids and bases?
- Al2O3
- ZnO
- PbO
- MgO
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Answer: D. MgO
Amphoteric oxides are those that react with both acids and bases. Aluminium oxide (Al2O3), zinc oxide (ZnO), and lead(II) oxide (PbO) are amphoteric. Magnesium oxide (MgO) is a basic oxide and reacts with acids but not with bases.
Anode mud in the electrolytic refining of copper contains:
- More reactive metals like zinc
- Less reactive metals like silver, gold, and platinum
- Copper oxides
- Impurities like sulphur and nitrogen
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Answer: B. Less reactive metals like silver, gold, and platinum
During electrolytic refining of copper, the impure copper acts as the anode, and a thin strip of pure copper acts as the cathode. Impurities like zinc and iron, being more electropositive than copper, get oxidized and dissolve in the electrolyte. Less electropositive impurities like silver, gold, and platinum do not get oxidized and settle down at the bottom of the cell as anode mud, which is a valuable source of these metals.
The process of refining a metal by heating it to its melting point and then cooling it, allowing the impurities to settle down, is known as:
- Liquation
- Distillation
- Smelting
- Electrolysis
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Answer: A. Liquation
Liquation is a refining process used for metals that have a low melting point and do not oxidize easily. The impure metal is melted on a sloping surface. The molten metal flows down, leaving behind the non-volatile impurities, while the metal oxidizes in the air if it's a reactive metal. However, the basic principle is melting and separation based on melting points.
In the extraction of aluminium by the Hall-Héroult process, the electrolyte is a mixture of molten cryolite and alumina. The purpose of cryolite is to:
- Act as a reducing agent
- Increase the melting point of alumina
- Decrease the melting point of alumina and increase its conductivity
- Act as a flux to remove impurities
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Answer: C. Decrease the melting point of alumina and increase its conductivity
Alumina (Al2O3) melts at a very high temperature (over 2000°C). Cryolite (Na3AlF6) acts as a solvent for alumina and forms a molten mixture with a significantly lower melting point (around 900-1000°C). It also increases the electrical conductivity of the mixture, making electrolysis economically viable.