Calculatate the mass of compound (molar mass = `256 g mol^(-1)` be the dissolved in 75 g of benzene to lower its freezing point by ` 0 .48 k(k_(f) = 5. 12 k kg mol ^(-1)` .

Explanation

Given : `Delta T f = 0 . 4 K, Kf = 5.12 kg mol^(-1)`
` w_(1) = 75 gm, w_(2) = ?, M_(2) = 256 " gm mol" ^(-1)`
`Delta Tf = (1000Kfw_(2))/(M_(2)xxw_(1)) = (1000xx5.12xxw_(2))/(256xx75)`
` w_(2) = (256xx75)/(0.48xx1000xx5.12) = 1.8 gm`