The Total solution for NCERT class 6-12
Two elements A and B formcompounds having formula AB2┬аand AB4. When dissolvedin 20 g of benzene (C6H6),┬а
1 g of AB_2┬аlowers the freezing point by 2.3 Kwhereas 1.0 g of AB_4┬аlowers it by 1.3 K. The molar depression constant for benzene is 5.1 Kkg mol_тИТ1. Calculate atomic masses of A and B.
Subtracting equation (i) from(ii), we have
2y┬а= 85.28
тЗТ┬аy┬а= 42.64
Putting the value of тАШyтАЩin equation (1), we have
x┬а+ 2├Ч 42.64 = 110.87
тЗТ┬аx┬а= 25.59
Hence, the atomic masses of A andB are 25.59 u and 42.64 u respectively.