Equivalent weight of `H_(3)PO_(2)`, when it disproportionate into `PH_(3)` and `H_(3) PO_(3)` is

Options

A. `(5M)/(4)`
B. `(7M)/(4)`
C. `(3M)/(4)`
D. `(9M)/(4)`

Answer

C

Explanation

Writing in terms of half reactions
`{:(H_(3)overset(+1)(PO_(2))+4e^(-)tooverset(-3)(P)H_(3)" (Reduction)"),(underset("........................................................................")(H_(3)overset(+1)PO_(2)toH_(3)overset(+3)O_(3)+2e^(-)"]"xx2)("Oxidation")):}`
`3H_(3)PO_(2)overset(4e^(-))toPH_(3)+2H_(3)PO_(3)` n factor
`=("Molecular mass of species")/("No.of moles of electrons transferred per mole of species")`
`=(M)/(4//3)=(3M)/(4)`