Question

Almost all metals in nature are found as ionic compounds in ores instead of being in the pure state. Why? What must be done to a sample of ore to obtain a metal substance that has desirable properties?

Short answer

Metals are mostly found as ionic compounds in ores due to their reactive nature, forming stable compounds with elements like oxygen, sulfur, and carbon. To obtain a metal substance with desirable properties, a sample of ore undergoes smelting, which involves heating the ore in the presence of a reducing agent to extract the pure metal. Additional steps like refining, alloying, and forming may be used to enhance the properties of the pure metal substance to tailor it for specific applications.

Step-by-step solution

Understand the nature of metals

Most metals are found as ionic compounds in ores because they are reactive and readily form stable compounds with other elements. In nature, they combine with oxygen, sulfur, carbon or other elements to create various minerals. For example, iron exists in the form of iron oxide like hematite (Fe2O3) and magnetite (Fe3O4), and copper appears as copper sulfides such as chalcopyrite (CuFeS2) and covellite (CuS).

Recognize the purpose of extracting metal from ores

The goal when extracting metals from ores is to obtain a pure metal substance with desirable properties for industrial and commercial applications. These properties include high electrical and thermal conductivity, ductility, malleability, and resistance to corrosion.

Extracting metals using smelting

One common process to extract metals from ores is smelting. Smelting involves heating the ore in a furnace in the presence of a reducing agent (usually carbon in the form of coke or charcoal) to reduce the metal oxide/sulfide to its elemental form. This reduction process removes oxygen/sulfur from the metal and produces pure metal and waste slag. For example, in the case of iron, the following reactions take place during the smelting process: \[ Fe2O3(s) + 3CO(g) \rightarrow \ 2Fe(l) + 3CO2(g) \]

Obtain the desired metal properties

Once the metal is extracted, additional steps like refining, alloying, and forming may be used to enhance the properties of the pure metal substance. These processes are designed to minimize impurities, change the metal structure, and tailor its properties for specific applications. For example, steel, which is an alloy of iron and carbon, is produced by controlling the amount of carbon in the iron and adding other elements like chromium, nickel, and manganese to impart specific properties like strength and corrosion resistance.