The correct option is C 0.7
In benzene, two molecules of ethanoic acid associate to form a dimer.
2CH3COOH⇌(CH3COOH)2
Initial a 0At.eq a(1−α) aα2
Number of moles at eq. neq=a(1−α+α/2)
At 60 % association α=0.6
∴neq=a(1−0.6+0.3)=a(0.7)
van't Hoff factor i = number of solute particles in solutiontheoritical number of solute particles
i=a(0.7)a=0.7