Problem 9 - 43 Years JEE ADVANCED (1978-2020) + JEE MAIN Chapterwise & Topicwise Solved Papers Chemistry

Question

The correct statement is : [Main April 10, 2019 (II)] (a) aniline is a froth stabilizer. (b) zincite is a carbonate ore. (c) sodium cyanide cannot be used in the metallurgy of silver. (d) zone refining process is used for the refining of titanium.

Step-by-Step Solution

Answer

Statement (a) is correct; others are incorrect.

Step 1: Analyze Option A

First, let's analyze statement (a). Aniline is a froth stabilizer used in the froth flotation process, which helps in stabilizing the froth formed during the extraction of metals like copper and lead. Thus, this statement is correct.

Step 2: Evaluate Option B

Next, consider statement (b). Zincite is not a carbonate ore; it is actually an oxide ore of zinc (ZnO). Therefore, this statement is incorrect.

Step 3: Examine Option C

Now, review statement (c). Sodium cyanide is indeed used in the metallurgy of silver to extract the metal through the cyanide process, also known as the MacArthur-Forrest process. Hence, this statement is incorrect.

Step 4: Assess Option D

Finally, evaluate statement (d). The zone refining process is primarily used for metals like silicon, germanium, and gallium arsenide, which require high purity. Titanium is refined through other processes, such as the Kroll process, not zone refining. Thus, this statement is incorrect.

Key Concepts

Froth Flotation

Froth flotation is a widely used process in the extraction of metals from their ores. In this method, the finely ground ore is mixed with water to form a slurry. This slurry is then treated with certain chemicals that make the desired minerals hydrophobic. This means that the minerals don't mix well with water and instead attach themselves to air bubbles that are introduced into the slurry.

The froth or foam created at the surface is where the minerals concentrate. These mineral-laden bubbles are then skimmed off for further processing.

• Used for sulfide ores of copper, lead, and zinc.
• Collectors, like pine oil, increase the non-wettability of the mineral particles.
• Froth stabilizers, such as aniline and cresol, help maintain the froth's stability to allow the enrichment of mineral particles.

Understanding how froth flotation works can help refine the extraction methods and improve recovery rates of different minerals.

Zone Refining

Zone refining is a sophisticated method designed to purify metals to an extremely high degree. Suppose you have a metal rod that contains impurities. In zone refining, a heat source is slowly moved along the rod, producing a molten zone that travels with the heat source. As the zone moves, it redistributes the impurities, ideally collecting them at one end of the rod.

This process can be repeated several times, allowing impurities to migrate further to one end while leaving the rest of the rod highly purified.

• Used mainly for semiconductors such as silicon and germanium.
• Requires highly controlled conditions to ensure purity is achieved.
• Not suitable for metals like titanium, which are refined through different processes like the Kroll process.

Zone refining is crucial for applications in electronics and photonics, where material purity is essential to performance.

Cyanide Process

The cyanide process, also known as the MacArthur-Forrest process, is a crucial technique for extracting gold and silver from their ores. The process involves: mixing finely ground ore with a dilute solution of sodium or potassium cyanide.

The cyanide compounds have a high affinity for these metals and can form soluble complexes, making it easier to extract the precious metals from the ore matrix.

• Sodium cyanide is typically used for extracting silver.
• The process includes subsequent steps to recover the pure metal, such as precipitation using zinc dust.
• Safety and environmental precautions are critical due to toxicity of cyanide compounds.

This method has revolutionized the field of metallurgy by significantly enhancing the yield of precious metals, though it requires careful handling and environmental management.