Question

Ores mined from the earth are usually contaminated with large amounts of impurities such as soil, sand, etc., called gangue. The impurities must be removed from the ore prior to the extraction of the metal. The processes Several steps are involved in the extraction of pure metal from ores. Metals and Non-metals used for removing the gangue from the ore are based on the differences between the physical or chemical properties of the gangue and the ore. Different separation techniques are accordingly employed.

Select the correct statements. I. Oxide ores of heavy metals are concentrated by hydraulic washing. II. Froth floatation process is used for the concentration of magnetic ores. III. Oxides of highly reactive metals can be reduced to metals by the action of heat alone. IV. Carbonate ores are decomposed to form metal oxides by heating in the absence of air.