Equivalent weight of H3PO2 when it disproportionate into PH3 and H3PO3 is:

The disproportionation reaction is 3H3PO2 → PH3 + 2H3PO3.Now the conversion of H3PO2 to PH3 involves the addition of 4 electrons.     n factor = no. of electrons involvedtotal no of molecules involved=43Hence, equivalent weight= m.wtn-factor=M×34