Question

Vitamin K is involved in normal blood clotting. When 1.91 g of vitamin K is dissolved in 25.0 g of camphor, the freezing point of the solution is lowered by 6.40 °C. The freezing point and Kf constant for camphor can be found here. Calculate the molar mass of vitamin K.

Answer 1

a) Massof solute = 1.91 g vitamin K

b ) T_f= 6.40 degC

c)Formula;

               T_f=K_f m

Where   T_f is the depression in freezing point

            K_f molal depression constant of thesolvent

              mmolality

       m = T_f/K_f

           =6.40 ⁰C/ 37.8 degC/m

          =0. 169 m

d) T_f=K_f m i

    From that m value found to be 0.169 m.

   molality =no.of mols of solute/1Kg of solvent

   0.16 mol/Kg = no.of mols of solute/0.025

   no.ofmols of solute =0.169 x 0.025

                                 =0.00423 moles

e) molar mass ofthe solute =mass of solute/no.of mols of solute

                                        = 1.91 g/0.00423 mols

                                         =451.5 g/mol