(a). What is the equivalent weight of `H_3PO_2` when it disproportionates into `PH_3` and `H_2PO_3`?
(b). What ist he equivalent weight of `H_3PO_2` when it acts as an acid?

Explanation

(a). Mw of `H_2PO_2=3xx1+31+2xx16=66`
`4e^(-)+H_3PO_2toPH_3`
`H_2PO_2toH_3PO_3+2e^(-)`
`Ew=((Mw)/(4)+(Mw)/(2))=Mw((1)/(4)+(1)/(2))`
`=(3Mw)/(4)=(3)/(4)xx66=49.5`
(b). `H_3PO_2` in monobasic acid
so it gives one `H^(o+)`
`Ew=(Mw)/(1)=66`.