Solutions Question 347

Question: A solution containing 0.85 g of ZnCl2 in 125.0 g of water freezes at 0.23C . The apparent degree of dissociation of the salt is ( Kf for water =1.86Kkgmol1 , atomic mass: Zn = 65.3 and Cl = 35.5)

Options:

A) 1.36%

B) 73.5%

C) 7.35%

D) 2.47%

Show Answer

Answer:

Correct Answer: B

Solution:

Mol.wt.=Kf×w×1000ΔTf×W

=1.86×0.85×10000.23×12555g Where w=0.85g

W=125g

ΔTf=0C(23C)=23C Now, i=MnormalMobserved=136.355=2.47

ZnCl21α,Znα,+++2Cl2α, Van’t Hoff factor (i) =1α+α+2α1=2.47
,α=0.735=73.5



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