Show graphically that the freezing point of a liquid will be depressed when a non-volatile solute is dissolved in it. The freezing point of a solution containing 0-3 g of acetic acid in 30-0 g of benzene is lowered by 0-`45^@`. Calculate the van't Hoff factor. (K for benzene = 5-12 K kg mol`""^(-1)`).

Explanation

Graphical representation of freezing point depression is given in Fig.
. Freezing point depression,
`Delta T_f =T_(f_f^(@) -T_f`
Let us first calculate observed molar mass.
`M_B=(K_fxxW_Bxx1000 )/( Delta T_f xx W_A)`
`=(5.12 xx 0.3 xx 1000)/(=5.12 xx 0.3 xx 1000)/(0.45 xx 30.0 )`
`113.8`

Normal molar mass of CH3COOH = 60
Van.t Hoff factor, i = `("Normal molar mass")/("Observed molar mass ")`
`=(60)/(113.8)= 0.527`