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Molecules of benzoic acid (C(6)H(5)COO...

Molecules of benzoic acid `(C_(6)H_(5)COOH)` dimerise in benzene. ‘w’ g of the acid dissolved in 30g of benzene shows a depression in freezing point equal to 2K. If the percentage association of the acid to form dimer in the solution is 80, then w is : (Given that `K_(f)=5K Kg "mol"^(-1)` Molar mass of benzoic acid `=122 g "mol"^(-1)`)

A

`2.4g `

B

`1.8g`

C

`1.0g `

D

`1.5 g `

Text Solution

Verified by Experts

The correct Answer is:
A
`{:(2A,rarr,(A)_2),(1,,-),(1-0.8,,(0.8)/2):}`
`DeltaT_f=K_f xxixxm`
`2=5xx0.6 xxw/(122)xx1000/30implies w=2.44g`
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