Respuesta :
Answer: The molecular weight of unknown non-electrolyte is 61.75 g/mol
Explanation:
Depression in freezing point is defined as the difference in the freezing point of water and freezing point of solution.
[tex]\Delta T_f=\text{Freezing point of benzophenone}-\text{Freezing point of solution}[/tex]
To calculate the depression in freezing point, we use the equation:
[tex]\Delta T_f=iK_fm[/tex]
or,
[tex]\text{Freezing point of benzophenone}-\text{Freezing point of solution}=iK_f\times \frac{m_{solute}\times 1000}{M_{solute}\times W_{solvent}\text{ (in grams)}}[/tex]where,
i = Vant hoff factor = 1 (for non-electrolyte)
[tex]K_f[/tex] = molal freezing point depression constant = 9.80°C/m
[tex]m_{solute}[/tex] = Given mass of unknown non-electrolyte = 1.0223 g
[tex]M_{solute}[/tex] = Molar mass of unknown non-electrolyte = ?
[tex]W_{solvent}[/tex] = Mass of solvent (benzophenone) = 10.2685 g
Putting values in above equation, we get:
[tex]47.5-31.7=1\times 9.80\times \frac{1.0223\times 1000}{M_{solute}\times 10.2685}\\\\M_{solute}=\frac{1\times 9.80\times 1.0223\times 1000}{15.8\times 10.2685}=61.75g/mol[/tex]
Hence, the molecular weight of unknown non-electrolyte is 61.75 g/mol
