Respuesta :
Answer: Molar mass of X is 106 g/mol
Explanation:
Depression in freezing point is given by:
[tex]\Delta T_f=i\times K_f\times m[/tex]
[tex]\Delta T_f=T_f^0-T_f=(3.6-3.2)^0C=0.4^0C[/tex] = Depression in freezing point
i= vant hoff factor = 1 (for non electrolyte)
[tex]K_f[/tex] = freezing point constant = [tex]1.86^0C/m[/tex]
m= molality
[tex]\Delta T_f=i\times K_f\times \frac{\text{mass of solute}}{\text{molar mass of solute}\times \text{weight of solvent in kg}}[/tex]
mass of solute = 908.0 mg = 0.9080 g (1g=1000mg)
Weight of solvent (dibenzyl ether)= 40.0 g = 0.04kg
Molar mass of solute (KCl) = 74.5 g/mol
Mass of solute = ?
[tex]0.4^0C=1\times 1.86\times \frac{0.9080g}{Mg/mol\times 0.0400kg}[/tex]
[tex]M=106g/mol[/tex]
Thus the molar mass of X is 106 g/mol
