Which of the following is true of lime-based flux used in metallurgy?

• A. It reacts with silica to form a slag that can be easily removed.
• B. It is used to oxidize impurities in the metal.
• C. It acts as a reducing agent in the extraction process.
• D. It increases the melting point of the ore.

Answer: (A)

Verified step by step guidance

1. Understand the role of flux in metallurgy: Flux is a substance added during the smelting process to help remove impurities from the metal ore.
2. Recognize that lime-based flux primarily consists of calcium oxide (CaO), which is basic in nature and reacts with acidic impurities.
3. Identify silica (SiO2) as a common acidic impurity found in metal ores, which can combine with lime to form calcium silicate (CaSiO3), a slag.
4. Know that this slag is molten at smelting temperatures and is less dense than the molten metal, allowing it to be easily separated and removed.
5. Conclude that the main function of lime-based flux is to react with silica impurities to form a removable slag, rather than oxidizing impurities, acting as a reducing agent, or increasing the melting point.