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Arrange the following aqueous solutions in terms of freezing point depression with the least depression first: 0.45m CaCl2, 0.45m glucose or 0.45m NaCl? Then determine the freezing point depression for each. For water, Kf=1.86 C/m

Respuesta :

Explanation:

Relation between [tex]k_{f}[/tex], molality and temperature is as follows.

                 T = [tex]K_{f} \times m \times i[/tex]

It is also known as depression between freezing point where, i is the Van't Hoff factor.

Let us assume that there is 100% dissociation. Hence, the value of i for these given species will be as follows.

          i for [tex]CaCl_{2}[/tex] = 3

           i for glucose = 1

           i for NaCl = 2

Depression in freezing point will have a negative sign. Therefore, d

depression in freezing point for the given species is as follows.

        [tex]T_{CaCl_{2}} = -1.86 \times 0.45 \times 3[/tex]

                  = [tex]-2.511^{o}C[/tex]

        [tex]T_{glucose} = 1.86 \times 0.45 \times 1[/tex]

                   = [tex]-0.837^{o}C[/tex]

       [tex]T_{NaCl} = -1.86 \times 0.45 \times 2[/tex]

                    = [tex]-1.674^{o}C[/tex]

Therefore, we can conclude that given species are arranged according to their freezing point depression with the least depression first as follows.

                     Glucose < NaCl < [tex]CaCl_{2}[/tex]