Name two metals which occur in nature in free state as well as in combined state.

37 Give the name and chemical formula of one ore of copper. 37 How is zinc extracted from its carbonate ore (calamine)? Explain with equations. 38 Name one ore of manganese. Which compound of manganese is present in this ore ? Also write its chemical formula. 38 A zinc ore on heating in air forms sulphur dioxide. Describe briefly any two stages involved in the conversion of this concentrated ore into zinc metal.