Question

What mass of dichloromethane (CH₂Cl₂) should be dissolved 20.9 moles of dihydrogen monoxide (H₂O) for the resulting solution to have a freezing point of -0.0183 degrees Celcius? The freezing point of pure dihydrogen monoxide is 0.00 degrees Celcius and K_f = 1.86 degrees Celcius/m.

Answer 1

T_F= ixk_fxmolality. By using this formula we can calculate weight of the solute (DCM).

         From data k_f=1.86   T_F=T₀-T =0⁰- (-0.0183)= 0.0183⁰ C.

                         molality= (w/mwt)1000/W.

                                       (w/84.93)x1000/18x20.9.

                                        = (w/84.93)x2.658

                                   T_F= ixk_fxmolality.

                                      0.0183=1.86x(w/84.9)x2.658

     weight of DCM= 0.0183X84.93/(2.658X1.86)

                              =1.554/4.943

                             =.314 gm