Elements A and B form two compounds B As andB.A. 0.05 moles of B2As we

1.	Elements A and B form two compounds B As andB.A. 0.05 moles of B2As weight 9.0 gms and0.10 mole of B2A weight 10 gms atomic weight ofA and B are-(1) 20 and 30(3) 40 and 302(2) 30 and 40(4) 30 and 20
Answer» let the molar mass of A be x and B be y so, ATQ 0.05(3x+2y) = 9=> 3x+2y = 180.......(1) and 0.1(x+2y) = 10=> x+2y = 100......(2) now subtracting 2 from 1 => 3x -x = 180-100=> 2x = 80. , so x = 80/2 = 40 and hence y = (100-40)/2 = 30.. so , option 3.

Elements A and B form two compounds B As andB.A. 0.05 moles of B2As weight 9.0 gms and0.10 mole of B2A weight 10 gms atomic weight ofA and B are-(1) 20 and 30(3) 40 and 302(2) 30 and 40(4) 30 and 20

Answer»

let the molar mass of A be x and B be y

so, ATQ 0.05*(3x+2y) = 9=> 3x+2y = 180.......(1)

and 0.1*(x+2y) = 10=> x+2y = 100......(2)

now subtracting 2 from 1 => 3x -x = 180-100=> 2x = 80. , so x = 80/2 = 40

and hence y = (100-40)/2 = 30..

so , option 3.