2g of benzoic acid (`C_6H_5COOH`) is dissolved in 25g of benzene show depression in freezing point equal to 1.62K. Molar depression constant for benzene, `K_f`=4.9K `kg mol^-1`. What is percentage association of acid if it forms a dimer in solution?

Explanation

Mass of solute = 2 g
Mass of solvent = 25 g
`DeltaT_(f)=1.62^(@)CrArrK_(f)=4.9`
`DeltaT_(f)=ixxK_(f)=W_(B)/(M_(B))xx1000/(W_(A))rArr1.62=ixx4.9xx2/(122)xx1000/(25)`
`i=(1.62xx122xx25)/(4.9xx2xx1000),i=0.504`
For association `alpha=(i-1)/(1/(n)-1)rArralpha=(0.504-1)/(1/(2)-1)=(-0.496)/(-0.5)=0.9916`
Percentage association = 99.16%