This problem is providing us with the mass of urea, 2.02 g as a non-electrolyte solute with a molar mass of 60.06 g/mol, which is dissolved in 25.0 g of an unknown solvent which freezes at 36.3 °C when pure. Thus, the freezing point constant of the solvent is required when it freezes at 34.7 °C due to the addition of urea; turning out to be 1.05 °C/m according to:
In chemistry, colligative properties are used to understand how the properties of a solvent change as a solute is added, forming a solution. In this case, we can use the following formula:
[tex](T_f^{solution}-T_f^{solvent})=-i*m*Kf[/tex]
Thus, since this problem is based on a non-electrolyte solute, we set the van't Hoff's factor as 1. Next, we calculate the molality of the solution with:
[tex]m=\frac{2.02g*\frac{1mol}{60.06g} }{25.0g*\frac{1kg}{1000g} } =1.53m[/tex]
Hence, we solve for Kf in the freezing point depression equation to obtain the following:
[tex]Kf=\frac{(T_f^{solution}-T_f^{solvent})}{-m}\\ \\Kf=\frac{34.7\°C-36.3\°C}{-1.53m}\\ \\Kf=1.05\°C/m[/tex]
Learn more about colligative properties: https://brainly.com/question/10323760
