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Write preparation of dichlorine (Cl_2). |
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Answer» Solution :(A) General Methods : By heating manganese dioxide with concentrated hydrochloric acid. `MnO_2 + 4HCl toMnCl_2 + Cl_2 + 2H_2O` However, a mixture of common salt and concentrated `H_2SO_4` is used in place of HCl `4NaCl + MnO_2 + 4H_2SO_4 toMnCl_2 + 4NaHSO_4 + 2H_2O + Cl_2` By the action of HCl on POTASSIUM permanganate. `2KMnO_4 + 16HCl 2KCl + 2MnCl_2 + 8H2_O + 5Cl_2` (B) Manufacture of DICHLORINE : (i) Deacon.s process: By oxidation of hydrogen chloride gas by atmospheric oxygen in the presence of `CuCl_2` (catalyst) at 723 K. `4HCl + O_2CuCl_2 gt2Cl_2 + 2H_2O` (ii) Electrolytic process : Chlorine is obtained by the electrolysis of brine (concentrated NaCl solution). Chlorine is liberated at anode. It is also obtained as a by product in many chemical industries. Anode : `2Cl_(aq) toCl_2(g) + 2e^(-)` Chlorine was discovered in 1774 by Scheele by action ofHCl on `MnO_2`. In 1810, Davy established its elementary nature and suggested the name chlorine on account of its COLOUR (Greek, Chloros = Greenish Yellow). |
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