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Many metals occur in the earth's crust as sulphides. To extract metals, the sulphide ores are first roasted in a reverberatory furnace in excess of air when metal oxide is formed and sulphur dioxide is released. Sulphur dioxide is a major air pollutant. It produces acid rain which damages crops, iron structures and buildings/histrorical monuments made up of marble. Now answer the following questions : (i) Name three important sulphide ores. (ii) What is acid rain ? How does it damage crops, iron structures and buildings made up of iron ? (iii) As a student of chemistry, what steps do you propose to control air pollution. |
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Answer» Solution :(i) Galena (PbS) is the sulphide ore of lead, Zinic blende (ZnS) is the sulphide ore of zinc and copper pyrites `(CuFeS_(2))` is the sulphide ore of copper. (ii) Rain water containing `H_(2)SO_(4) and HNO_(3)` is called ACID rain. `SO_(2)` produced as a result of roasting, first gets oxidised in air to form `SO_(3)` which subsequently dissolves in water to form `H_(2)SO_(4)` acid. `{:(""2ZnS + 3 O_(2) rarr 2 ZnO + 2 SO_(2)" ",),(2SO_(2) + O_(2) underset("or METAL ions")overset("NO, root")(rarr) 2 SO_(3)),(""SO_(3) + H_(2)O rarr H_(2)SO_(4)):}` The `H_(2)SO_(4)` thus produced increases the acidity of the soil which kills the microbes present in the soil and thus decreases the fertility of the soil. `H_(2)SO_(4)` also reacts with iron and marble thereby damaging iron structures and building made upon of marble. `{:(""Fe+H_(2)SO_(4) rarr FeSO_(4)+H_(2)" ",),(CaCO_(3) + H_(2)SO_(4)rarr CaSO_(4) + CO_(2) + H_(2)O):}` (iii) `SO_(2)` produced as a result of roasting should not be released into the atmosphere. It should be collected and converted into useful PRODUCTS like `Na_(2)SO_(3), H_(2)SO_(4)`, etc. `SO_(2) + 2 NaOH rarr Na_(2)SO_(3) + H_(2)O` |
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