What is the name of the process that converts sulphide ores into oxides by heating strongly in the presence of excess air?

The correct answer is B, Roasting. Roasting means heating a sulphide ore strongly in plenty of air, so that the sulphide turns into an oxide and the sulphur escapes as sulphur dioxide gas. The standard example is zinc blende: 2ZnS + 3O2 gives 2ZnO + 2SO2. An oxide is easier to reduce to the metal with carbon, which is why ores of zinc, lead and copper first pass through this step. Remember the key contrast: roasting uses excess air and suits sulphide ores, while calcination uses limited or no air and suits carbonate ores. A is wrong, because calcination heats carbonate ores such as calamine in limited air, as when ZnCO3 gives ZnO and CO2. C is wrong, because smelting is the later step in which the oxide is reduced to metal in a furnace with a reducing agent and a flux. D is wrong, because incineration is burning waste at a high temperature, not a step in extracting metals. Exam tip: sulphide ore, roasting, excess air; carbonate ore, calcination, little or no air.