`12.2 g` of benzoic acid is dissolved in (i) `1 kg` acetone `(K_(b) = 1.9 K kg mol^(-1))` and (ii) 1 kg benzene `(K_(b) = 2.6 K kg mol^(-1)`.
The elevation of boiling points are `0.19^(@)C` and `0.13^(@) C`, respectively.
a. What are the molar masses of benzoic acid in the two solutions ?
, b. What are the structures of benzoic acid in the two solutions ?

Answer

(a) 122, (b) It means that benzoic acid remains as it is in acetone while it dimerises in benzene
`(##ALN_CHM_C08_E01_613_A01##)`

Explanation

(a) (i) `DeltaT_(b) = iK_(b).m`
`0.17 = ixx 1.7 xx (1.22//122)/(0.1)`
`L = 1 = ((mol ut)_(Th))/((mol ut)_(ACt))`
`(mol ut)_(ACt) = (122)/(1) gm//mol`
(ii) `DeltaT_(b) = ixx K_(b).m`
`0.13 = ixx 2.6 xx (1.22//122)/(0.1)`
`i=0.5 = ((mol ut)_(Th))/((mol ut)_(ACt)) rArr (mol ut)_(Act) = (122)/(0.5)`
`= 244 gm//mol`
(b) In Acetone its normal ie but in benzene it is in dimenc form