Respuesta :
Answer:
The molar mass of the unknown compound is 153.3 g/mol
Explanation:
Step 1: Data given
Mass of an unknown molecular compound = 27.6 grams
Mass of benzene = 0.250 kg
Kf of benzene = 5.12 °C/m
freezing point depression of 3.69 °C
Step 2: Calculate molality
ΔT = i*Kf*m
⇒with ΔT = reezing point depression of 3.69 °C
⇒with i = the van't Hoff factor of Benzene = 1
⇒with Kf = 5.12 °C/m
⇒ with m = molality = moles unknown compound / mass of benzene
3.69 = 1 * 5.12 * m
m = 0.72 molal
Step 3: Calculate moles of the unknown compound
molality = moles / mass benzene
0.72 molal = moles / 0.250 kg
Moles = 0.72 m * 0.250 kg
Moles = 0.18 moles
Step 4: Calculate molar mass of the unknown compound
molar mass = mass / moles
Molar mass = 27.6 grams / 0.18 moles
Molar mass = 153.3 g/mol
The molar mass of the unknown compound is 153.3 g/mol
Molar mass is the mass of the one mole of substance. The molar mass of the given unknown compound is 153.3 g/mol.
Molality of the compound can be calculated using
ΔT = i Kf m
Where,
ΔT = freezing point depression = 3.69 °C
i = Van't Hoff factor of Benzene = 1
Kf = constant of freezing = 5.12 °C/m
m = molality = ?
Put the values in the equation,
3.69 = 1 x 5.12 x m
m = 0.72 molal
Number of moles of the compound,
[tex]\bold {molality =\dfrac { moles} { mass\ benzene}}\\\\\bold {0.72\ molal = \dfrac {moles }{0.250\ kg}}\\\\\bold {Moles = 0.72\ m \times 0.250\ kg}\\\\\bold {Moles = 0.18}[/tex]
So, molar mass of the unknown compound,
[tex]\bold {Molar\ mass =\dfrac { mass}{ moles}}\\\\\bold {Molar\ mass = \dfrac {27.6\ grams }{0.18\ moles}}\\\\\bold {Molar\ mass = 153.3 g/mol}[/tex]
The molar mass of the given unknown compound is 153.3 g/mol.
To know more about molar mass,
https://brainly.com/question/12127540
