The vapour pressure of two miscible liquids A and B are 300 and 500 mm of Hg respectively.In a flask 2 moles of A are mixed with 6 moles of B.Further to the mixture, 32 g of an ionic non-volatile solute MCl (partically ionised mol.mass =70 u) were also added.Thus, the final vapour pressure of solution was found to be 420 mm of Hg.Then, identify the correct statement(s): (Assume the liquid mixture of A and B to behave ideally ).

The vapour pressure of two miscible liquids A and B are 300 and 500 mm

1.	The vapour pressure of two miscible liquids A and B are 300 and 500 mm of Hg respectively.In a flask 2 moles of A are mixed with 6 moles of B.Further to the mixture, 32 g of an ionic non-volatile solute MCl (partically ionised mol.mass =70 u) were also added.Thus, the final vapour pressure of solution was found to be 420 mm of Hg.Then, identify the correct statement(s): (Assume the liquid mixture of A and B to behave ideally ).
Answer» The numerical value of RELATIVE lowering in vapour pressure upon ADDITION of solute MCl is `1//15` The solute MCl is 25% ionised in the above question The solute MCl is 23.33% ionised in the above question Upon addition of excess `Pb(NO_3)_2`, the NUMBER of moles of `PbCl_2` precipitated is `2//35` Solution :`P_0=X_AP_A^@+X_BP_B^@=2/8xx300+6/8xx500`=450 mm of Hg Now, RLVP=`(P_0-P_S)/P_0=(450-420)/450=1/15` Also, RLVP =`(("in")/("in"+N))` `1/15=((32i)/70)/((32i)/70+8) :. i=1.25=(1+(2-1)alpha)`. So `alpha=0.25` (or 25 %) `:. n_(Cl^(-))` produced `=25/100xx32/70=4/35` `:. n_(PbCl_2)` precipitated =`1/2xx4/35=2/35`