Animated Solution for Chemistry - Metallurgy: The correct statement is

Metallurgy is a fascinating blend of physical processes and precise chemical reactions. In this problem, we are presented with four distinct statements covering various metallurgical concepts—from refining techniques to ore identification and extraction processes. Our mission is to evaluate each statement and uncover the single truth hidden among them.

The Zone Refining Myth

The first statement claims that the zone refining process is used for the refining of titanium. Let's break this down. Zone refining is an elegant technique based on the principle that impurities are more soluble in the molten state of a metal than in its solid state. It is exclusively used to obtain ultra-pure semiconductors like silicon ($Si$), germanium ($Ge$), boron ($B$), gallium ($Ga$), and indium ($In$).

Titanium ($Ti$), on the other hand, is highly reactive with oxygen and nitrogen at high temperatures. To purify it, we rely on the van Arkel method, where impure titanium is heated with iodine to form a volatile complex ($Ti{I}_4$), leaving impurities behind. Therefore, statement (a) is completely incorrect.

The Identity of Zincite

Next, we look at statement (b), which labels zincite as a carbonate ore. In metallurgy, knowing the chemical formulas of common ores is non-negotiable. Zincite is actually an oxide ore with the chemical formula $ZnO$.

If we were looking for the carbonate ore of zinc, we would be talking about calamine, which has the formula $ZnC{O}_3$. Because zincite is an oxide and not a carbonate, statement (b) is also false.

Silver and Cyanide

Statement (c) boldly asserts that sodium cyanide ($NaCN$) cannot be used in the metallurgy of silver. This is a classic trap! The extraction of silver heavily relies on the MacArthur-Forrest cyanide process.

In this hydrometallurgical process, silver sulfide ore ($A{g}_{2}S$) is leached with a dilute solution of sodium cyanide in the presence of air. The reaction forms a highly soluble complex:

Because sodium cyanide is absolutely essential for leaching silver, statement (c) is factually incorrect.

The Magic of Froth Floatation

Finally, we arrive at statement (d), which states that aniline is a froth stabiliser. Let's visualize the froth floatation process, which is primarily used to concentrate sulfide ores.

In the floatation tank, we add collectors like pine oil or fatty acids. These chemicals selectively coat the ore particles, making them hydrophobic (water-repellent) so they can attach to rising air bubbles. However, the froth formed at the surface can be quite fragile. To prevent the bubbles from bursting before the ore can be skimmed off, we add froth stabilisers.

The most common and effective froth stabilisers used in the industry are aniline and cresols. They reduce the surface tension of water, ensuring the froth remains stable and intact.

After a thorough investigation of all four options, it is clear that statement (d) is the only scientifically accurate claim. This problem serves as a brilliant reminder to carefully memorize the specific roles of reagents and the exact applications of refining methods in metallurgy.