Elements A and B form two compounds `B_2​A_3` and `B_2​A`. If 0.05 moles of `B_2​A_3` weigh 9.0 g and 0.10 mole of `B_2​A` weigh 10 g, then atomic weight of A and B are :-

Options

A. 20 and 30
B. 30 and 40
C. 40 and 30
D. 30 and 20

Answer

C

Explanation

Let at. Wt of A = a
at.wt of B = b
wt of 1 mole of `B_(2)A_(3)=180 gm`
`2xx b+3xa=180" …………(1)"`
wt of 1 mole of `B_(2)A=100 gm`
`2xxb+1xxa=100 gm`
`2xxb+1xxa=100" …………(2)"`
by applying `(1)-(2)`
`2a=80 rArr a=40`
Substitute value of a in (2)
`2b=60" "rArr b=30`