Red lead, Pb3O4, reacts with concentrated HCl as Pb3O4 + 8HCl -> 3PbCl2 + Cl2 + 4H2O. Of the 8 mol of HCl consumed per mol of Pb3O4, the number of moles that are oxidised is

JEE Advanced levelSingle correct optionDifficulty 3 of 3pb105

Red lead, $Pb X_{3} O X_{4}$ , reacts with concentrated $HCl$ as $Pb X_{3} O X_{4} + 8 HCl 3 PbCl X_{2} + Cl X_{2} + 4 H X_{2} O$ . Of the 8 mol of $HCl$ consumed per mol of $Pb X_{3} O X_{4}$ , the number of moles that are oxidised is

Only the

PbO X_{2}

part (

+ 4

lead) is an oxidant, and it takes 2 electrons per Pb, oxidising 2

Cl X^{-}

to 1

Cl X_{2}

. So 2 mol of

HCl

are oxidised; the other 6 mol only supply

Cl X^{-}

for

PbCl X_{2}

(3 x 2) while the 4

H X_{2} O

account for the H and O. Check Cl:

6 + 2 = 8