Long Answer TypeBalance the following equation by oxidation number method:
(in alkaline medium)
(i) The skeleton equation along with oxidation number of each atom is
(ii) Noting the changein O.N. of above atoms,
Increase S = +4 to +6 i..e 2
Decrease Cr = +6 to +3 i.e. 3
(iii) Equalise the increase/decrease in O.N. by
multiplying 
(iv) Balance Cr atoms by multiplying [Cr(OH)4]- by 2 and balance S atoms by multiplying (SO4)2- by 3.
(v) Balance O atoms by adding three H2O molecules on the reactant side.
(vi) Balance the H atoms
Net charge on LHS = -4 - 6 = -10
Net charge on RHS = -2 -6 = -8
adding two OH-(basic medium) on RHS and adding 2 water molecules on the reactant side.
With the net ionic equation for the reaction of potassium dichromate (VI), K2Cr2O7 with sodium sulphite, Na2SO3, in an acid solution to give chromium (III) ion and the sulphate ion.
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