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The freezing point of a solution contain...

The freezing point of a solution containing `0*3` gms of acetic acid in 30 gms of benzene is lowered by `0*45 K`. Calculate the van't Hoff factor.
`(At. wt. of C = 12, H = 1, 0 = 16, K_f " for benzene " = 5.12 " K kg mole"^(-1)` ).

Text Solution

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Step 1. Calculation of observed molar mass of acetic acid `(CH_(3)COOH)`
`M_(2)=(K_(f) xx W_(2)xx1000)/(DeltaT_(f)xx W_(1))`
Here, `W_(B)=0.3g, W_(A)=30g, DeltaT_(f)=0.45K`
`K_(f)=5.12"K kg mol"^(-1)`
`M_(B)=((5.12"K kg mol"^(-1)) xx (0.3 g) xx 1000)/(0.45K xx 30g)`
`=113.78"g mol"^(-1)`
Step 2. Calculation of Van.t Hoff factor
Normal molar mass of `CH_(3)COOH`
`=12+3xx1+12+2xx16+1=60"g mol"^(-1)`
`i=("Normal molar mass")/("Observed molar mass")=(60)/(113.78)=0.527`
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