When white phosphorus (P4) is heated with concentrated NaOH solution in an inert atmosphere of CO2, we are told it gives a salt ' X ' and a gas ' Y '. Step 1: Recall the known reaction White phosphorus reacts with hot concentrated NaOH (and no oxygen) to produce phosphine gas (PH3) and sodium hypophosphite (NaH2PO2) as the salt: P4+3NaOH+3H2O→PH3+3NaH2PO2 Step 2: Identify ' X ' and ' Y ' Salt X=NaH2PO2 (sodium hypophosphite) Gas Y=PH3 (phosphine) Step 3: Find oxidation states of phosphorus in each For X=NaH2PO2 Let oxidation state of P=x. ‌(+1)+2(+1)+x+2(−2)=0 ‌1+2+x−4=0 ‌x=+1 So in NaH2PO2,P has oxidation state +1. For Y=PH3 Let oxidation state of P=x. x+3(+1)=0x=−3 Thus, in PH3,P has oxidation state −3.
