Multiple choice Which of the following pairs of ‘ore-corresponding chemical formula’ is wrong? Bauxite - Al2O3.3H2O Lanarkite - PbO.PbSO4 Crocoisite - PbCrO4 Cuprite - Cu2O Calamine - ZnCO3 Reveal answer Fill a bubble to check yourself A Correct answer Explanation Bauxite (Al2O3.2H2O) is the ore of aluminium. The chemical formula for gibbsite is Al2O3.3H2O.