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When 1 g of arsenic is added to 80 g of ...

When 1 g of arsenic is added to 80 g of benzene, the freezing point of benzene is lowered by `0.19^(@)C(K_(f)=4.9)`. The formula of arsenic is (At. wt. of As = 75 ) :

A

As

B

`As_(2)`

C

`As_(3)`

D

`As_(4)`

Text Solution

Verified by Experts

The correct Answer is:
D
Molecular mass of arsenic
`M=(K_(f)xx1000 xx w_(B))/(w_(A) xx Delta T_(f))=(4.9 xx 1000 xx 1)/(86 xx 0.19)=299.87`
No. of As atoms present per molecule
`=(299.87)/(75)=4`
Formula `=A s_(4)`
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