what are the normal freezing points and boiling points of th

what are the normal freezing points and boiling points of the following solutions?

A. 21.1g NaCl in 141 ml of water (Assume the van\'t Hoff factor (i) is equal to 1.8)

B. 15.5g of urea [(NH2)2CO] in 70.5 mL of water?

Solution

A) dT = i x k x m ,

m = ( 21.1/58.5) x ( 1000/141) = 2.558 = molality ,

dT = 0-Tf = 1.8 x 1.86 x 2.558, T f = -8.56 C

dT = Tb-100 = (1.8x0.512x2.558) , Tb = 102.357

B) m = ( 15.5/60) x( 1000/70.5) = 3.664, i = 1,

0-Tf = 1.86 x 3.664, Tf = -6.815 C,

Tb-100=0.512x3.664 , Tb = 101.876 C