Question

Two elements A and B fom compounds of formula AB₂ and AB₄. When dissolved in 20.0 g of benzene 1.0 g of AB₂ lowers f. pt. by 2.3°C whereas 1.0 g of AB₄ lowers f. pt. by 1.3°C. The K_f  for benzene is 5.1. The atomic masses of A and B are

(a) 25,42

(b) 42,25

(c) 52,48

(d) 48,52

Answer 1

Correct option (a) 25,42

Explanation:

Let the masses of A and B be a and b.The mass of AB₂ will be (a + 2b) g mol^-1 and AB₄ will be (a+4b) g mol^-1.