2. (15 pts) Coal-fired power plants and some metallurgical plants that treat sulfide ores or concentrates...

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2. (15 pts) Coal-fired power plants and some metallurgical plants that treat sulfide ores or concentrates generate SO2, which if emitted to the atmosphere may cause acid rain. One method for reducing sulfur dioxide emissions is to treat the hot gases with limestone (calcium carbonate). This decomposes thermally to lime upon exposure to hot gases containing SO₂: Hint: CaCO3 = CO2 + CaO The lime then reacts with the SO₂ to form calcium sulfate: SO₂ + CaO + 1/2O2 = CaSO4 Comment on the environmental soundness of this process (note that this question isn't in the textbook). The method has been less successful technically than anticipated; complete conversion of limestone to calcium sulfate is rare. The initial reaction rate on contacting sulfur dioxide, oxygen and lime is high, but the rate drops to zero after reaction has proceeded to some extent. Explain this drop in reaction in terms of your understanding of gas-solid reactions. Density (kg/m³) Molecular weights (g/mol) CaCO3 2930 88 CaO 3300 56 CaSO4 2610 136 Se 2. (15 pts) Coal-fired power plants and some metallurgical plants that treat sulfide ores or concentrates generate SO2, which if emitted to the atmosphere may cause acid rain. One method for reducing sulfur dioxide emissions is to treat the hot gases with limestone (calcium carbonate). This decomposes thermally to lime upon exposure to hot gases containing SO₂: Hint: CaCO3 = CO2 + CaO The lime then reacts with the SO₂ to form calcium sulfate: SO₂ + CaO + 1/2O2 = CaSO4 Comment on the environmental soundness of this process (note that this question isn't in the textbook). The method has been less successful technically than anticipated; complete conversion of limestone to calcium sulfate is rare. The initial reaction rate on contacting sulfur dioxide, oxygen and lime is high, but the rate drops to zero after reaction has proceeded to some extent. Explain this drop in reaction in terms of your understanding of gas-solid reactions. Density (kg/m³) Molecular weights (g/mol) CaCO3 2930 88 CaO 3300 56 CaSO4 2610 136 Se

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