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19.5 of CH2FCOOH is dissolved in 500 g of water. The depression in the freezing point of water observed is 10C. Calculate the van't Hoff factor and dissociation constant of fluoroacetic acid.
ChemistrySolutions
Solution:
2087 Upvotes Verified Answer
Using the relation,
=1000×1.86×19.5500×1=72.54 g mol1
M2( Calculated )=12+2+19+12+2×16+1
=78 g mol1
i=M2 (calculated) M2 (observed) =7872.54=1.0753.
Calculation of dissociation constant :
Let α be the degree of dissociation and C be the initial concentration of CH2FCOOH


i=C(1+α)C=1+αα=i1=1.07531=0.0753Ka=CαCαC(1α)=Cα21α
Taking the volume of solution as 500 mL
C=19.578500×1000M=0.5MKa=0.5×(0.0753)2(10.0753)=3.07×103

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