Iron (Fe) is obtained from rock that is extracted from

Chapter 5, Problem 80

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Iron (Fe) is obtained from rock that is extracted from open pit mines and then crushed. The process used to obtain the pure metal from the crushed rock produces solid waste, called tailings, which are stored in disposal areas near the mines. The tailings pose a serious environmental risk because they contain sulfides, such as pyrite , which oxidize in air to produce metal ions and ions that can enter into surface water or ground water. The oxidation of to is described by the unbalanced chemical equation below. Thus, the oxidation of pyrite produces and ions that can leach into surface or ground water. The H+ Fe3+ Fe3+1aq2 + SO4 2-1aq2 + H+1aq2 1not balanced2 leaching of ions causes the water to become very acidic. To prevent acidification of nearby ground or surface water, limestone is added to the tailings to neutralize the ions: (a) Balance the equation above for the reaction of and [Hint: Start with the half-equations and ] (b) What is the minimum amount of required, per kilogram of tailings, to prevent contamination if the tailings contain 3% S by mass? Assume that all the sulfur in the tailings is in the form