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Two elements A and B form compounds havi...

Two elements A and B form compounds having molecular formula `AB_(2)` and `AB_(4)`. When dissolved in 20g of benzene, 1g of `AB_(2)` lowers the fpt by 2.3K whereas 1g of `AB_(4)` lowers it by `1.3K (K_(f)` for `C_(6)H_(6) = 5.1 K m^(-1))` At. Mass of A and B are

A

`42.64` and `25.58`

B

`25.58` and `42.64`

C

`22.64` and `55.58`

D

`45.64` and `22.58`

Text Solution

Verified by Experts

The correct Answer is:
B
`2.3 = (5.1 xx 1 xx 1000)/((a+2b)xx 20)`
`a +2b = (51 xx 50)/(23)` ..(i)
Similary,
`a +4b = (51 xx 50)/(13)` ...(ii)
Subtracting (i) from (ii)
`2b = (51 xx 50 xx 10)/(13 xx 23)`
`b = 42.64`
Substituting in (i).
`a = 25.58`
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