Respuesta :
Answer:
The value of [tex]K_f[/tex] for xylene is 4.309°C/m.
The molar mass of pentane using this data is 73.82 g/mol.
Explanation:
[tex]\Delta T_f=K_f\times \frac{\text{Amount of solute}}{\text{Molar mass of solute}\times \text{Mass of solvent(kg)}}[/tex]
where,
[tex]\Delta T_f[/tex] =depression in freezing point
[tex]K_f[/tex] = freezing point constant
we have :
1) freezing point constant for xylene = [tex]K_f[/tex] =?
Mass of toluene = 0.193 g
Mass of xylene = 2.532 kg = 0.002532 kg ( 1 g =0.001 kg)
[tex]\Delta T_f=3.57^oC[/tex]
[tex]3.57^oC=K_f\times \frac{0.193 g}{92 g/mol\times 0.002532 kg}[/tex]
[tex]K_f=4.309^oC/m[/tex]
The value of [tex]K_f[/tex] for xylene is 4.309°C/m.
2)
Mass of pentane = 0.123 g
molar mass of pentame= M
Mass of xylene = 2.493 g = 0.002493 kg
Freezing point Constant of xylene = [tex]K_f=4.309^oC/m[/tex]
[tex]2.88^oC=4.309^oC/m\times \frac{0.123g}{M\times 0.002493 kg}[/tex]
M = 73.82 g/mol
The molar mass of pentane using this data is 73.82 g/mol.
