The balanced equations are(1) 2MnCl2​+5 K2​ S2​O8​+8H2​O→2KMnO4​+4 K2​SO4​+6H2​SO4​+4HCl(2) 2KMnO4​+5H2​C2​O4​+3H2​SO4​→K2​SO4​+2MnSO4​+8H2​O+10CO2​Given, mass of oxalic acid added =225mgSo, millimoles of oxalic acid added =90225​=2.5Now from Equation 2Millimoles of KMnO4​ used to react with oxalic acid=I andMillimoles of MnCl2​ required initially=1∴ Mass of MnCl2​ required initially =1×(55+71)=126mg