The ore of which metal is concentrated by leaching?

Which of the following reactions is suitable for concentrating ore by the leaching process?

Which among the following ores is concentrated by the froth flotation process?

The method of concentrating the ore which makes use of the difference in density between ore and impurities is called:

Which of the following ores is concentrated by the froth flotation process?

Sulphide ores of metals are usually concentrated by froth floatation process. Which one of the following sulphide ores offers an exception and is concentrated by chemical leaching?