To measure the quantity of `MnCl_(2)` dissolved in an queous solution, it was completely converted to `KMnO_(4)` using the reaction
`MnCl_(2)+K_(2)S_(2)O_(8)+H_(2)O to KMnO_(4)+K_(2)SO_(4)+HCl`(equation not balanced).
Few drops of concentrated HCl were added to this solution and gently warmed. Further , oxalic acid (225 mg) was added in portions till the colour of the permanganate ion disappeared. Calculate the quantity of `MnCl_(2)` (in mg) presence in the initial solution.
( Atomic weights in g `mol^(-1)`: Mn=55,Cl=35.5)

Explanation

`Eq. of MnCl_(2) = Eq. " oxalic acid" `
`w xx 5 /126 = 225/90 xx 2 implies w = 225 xx 2/90 xx 126/5 = 126 mg`