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The measured freezing point depression f...

The measured freezing point depression for a 0.1 m aqueous `CH_(3)COOH` solution is `0.19^(@)C`. The acid dissociation constant `K_(a)` at this concentration will be (Given `K_(f)`, the moala cryoscopic constant = 1.86 K Kg `mol^(-1))`

A

`4.76xx10^(-5)`

B

`4xx10^(-5)`

C

`8xx10^(-5)`

D

`2xx10^(-5)`

Text Solution

Verified by Experts

The correct Answer is:
B
`DeltaT_(f)=ixxk_(f)xxm`
`i=(0.19)/(1.86xx0.1)=1.02`
`alpha=(i-1)/(n-1)=(0.02)/(1)=2xx10^(-2)`
`k_(a)=calpha^(2)=1xx10^(-1)xx(2xx10^(-2))^(2)=4xx10^(-5)`.
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