Pure Benzene freezes at `5.4^@C.` A solution of 0.223 g of phenyl acetic acid `(C_6H_5CH_2COOH)` in 4.4 g of benzene `(K_f="5.12 K kg mol"^(-1))` freezes at `4.47^@С.` From this observation, one can conclude that

Options

A. phenyl acetic acid exists as such in benzene
B. phenyl acetic acid undergoes partial ionization in benzene
C. phenyl acetic acid undergoes complete ionization in benzene
D. phenyl acetic acid dimerizes in benzene

Answer

D

Explanation

`m= ((-Delta T_(f)))/(K_(f))= ((5.4 - 4.47))/(5.12) mol kg^(-1) ie.., (0.223 g//M)/((4.4 //1000)kg)= (0.93)/(5.12) mol kg^(-1)`
Solving for M, we get M= 279 g `mol^(-1)`, Number of molecules of phenyl acetic acid `=(279)/(136)=2`