The equivalent weight of Hypo in the reaction Na2 S2O3+Cl2+H2O→Na2SO4+2HCl+S  is [M = mol. wt]

Na2 S+22O3+Cl2+H2O→Na2S+6O4+2HCl+S0Total ox.state of sulphur/mole of Na2S2O3=+4Total ox.state of sulphur on RHS=+6+0 =+6Total increase in  ox.state of sulphur/mole of Na2S2O3=2∴ EW of Na2 S2O3.5H2O(Hypo)=M2Alternate method:                           In Na2S2O3 , ox.states of sulphur are -2 and +6                                        In Na2SO4 ox. state of sulphur = +6A sulphur atom with  '+6' ox.state in  Na2S2O3 doesn't show any change in ox.state.But the sulphur atom with  '-2' ox.state in  Na2S2O3  changes to zero (in sulphur)Thus Total increase in  ox.state of sulphur/mole of Na2S2O3=2∴ EWof Na2 S2O3=M2