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Sodium thiosulphate is prepared by :A. Boiling `Na_2SO_3` solution with elemental sulphur in alkaline mediumB. Boiling `Na_2SO_3` solution with elemental sulphur in acidic mediumC. Oxidation of poly sulphides , `Na_2S_3` with airD. Reduction of bisulphite solution plus `SO_2` with zinc dust |
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Answer» Correct Answer - A,C (A)`Na_2SO_3 + S underset(OH^- or H_2O)overset("boiling")toNa_2S_2O_3` (B)`S_2O_3^(2-)` formed in presence of acid precipitates sulphur and liberates `SO_2` gas according to the following reaction . `S_2O_3^(2-)+H^(=)tounderset("disproportionation")(Sdarr`(white) + `SO_2) uarr H_2O` (C )`2Na_2S_3 + 3O_2 underset("air")overset("heating")to2Na_2S_2O_3 + 2S` (D)`2HSO_3^(-)+SO_2overset(Zn)to S_2O_4^(2-)+SO_3^(2-)+H_2O` |
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