Two elements A&B form compounds of formula AB2 and AB4 then dissolved in 20.0 gm of benzene 1.0 gm AB2 lowers freezing point by 2.3degees celsius whereas 1.0 gm AB4 lowers freesing point by 1.3 degees celsius the Kf for benzene is 5.4 the atomic masses A and Bare respectively
