Which metal is produced by the Kroll process?

• A. Nickel
• B. Titanium
• C. Copper
• D. Chromium

Answer: (B)

The Kroll process is the industrial method used to produce metallic titanium by reducing titanium tetrachloride with magnesium. In this route, titanium ore is first converted to TiCl4, which is then purified and reacted with magnesium at high temperature in an inert environment to give titanium metal and magnesium chloride: TiCl4 + 2 Mg → Ti + 2 MgCl2. This approach works well because titanium forms a very stable oxide and direct reduction of its oxide is difficult, whereas converting it to a volatile chloride and reducing that chloride with magnesium yields metal more practically. The product comes out as a porous titanium sponge that is later purified and melted into ingots. Other metals like nickel, copper, or chromium are typically produced by different processes tailored to their chemistry, not by this chloride–magnesium reduction.