Give the reason

Dear student, Calcination process is used to convert carbonate ores to oxide with the release of carbon dioxide gas. The presence of the carbonate group makes it easier for the release of carbon dioxide. Thus, if oxygen is used the release of carbon dioxide would be difficult. So, calcination takes place in the absence of air. The calcination process normally takes place at temperatures below the melting point of the product materials. Roasting is the process of converting an ores to oxide by strongly heating it in the presence of excess of air . For example sulphide ores are converted into their respective oxide by heating in the presence of air. Hence due to this oxygen is needed. Regards