Calculate the amount of CaCl2, which must be added to 2 kg water so that the freezing point is depressed by 61 K (Kf of H2O =1.86 K kg mol^-1, Atomic mass of Ca = 40, Cl = 35.5)

Asked by jusu20111 | 26th Jan, 2020, 01:15: PM

Expert Answer:

Depression in freezing point can be calculated by-
 
increment T subscript f equals fraction numerator i cross times k subscript f cross times w subscript B over denominator w subscript A space end subscript space cross times space M subscript B end fraction
C a C l subscript 2 rightwards arrow C a to the power of plus 2 end exponent space space space plus 2 space C l to the power of minus
i equals 2
M subscript B equals M o l e c u l a r space M a s s space o f space C a C l subscript 2 space end subscript equals 40 plus 35.5 cross times 2 equals
61 equals fraction numerator 3 cross times 1.86 cross times w subscript B over denominator 111 cross times 2 end fraction

w subscript B equals fraction numerator 111 cross times 3 cross times 61 over denominator 2 cross times 1.86 end fraction equals 2426.8 space g

Answered by Ravi | 27th Jan, 2020, 12:12: PM