hen 9.3 g of an unknown non-electrolyte is dissolved in 50.0 g of benzene, the boiling point the boiling point increased to 81.19 degrees C from 80.1 degrees C. If the Kbp of the solvent is 2.53 K/m, calculate the molar mass of the unknown solute.
The answer is 432. I don't know how
delta T = Kb*molality
Solve for molality
molality = moles/kg solvent
Solve for moles.
moles = grams/molar mass
solve for molar mass.
To calculate the molar mass of the unknown solute, you need to apply the formula:
ΔT = Kbp * m * i
where:
ΔT = boiling point elevation (in degrees Celsius)
Kbp = boiling point elevation constant of the solvent (in degrees Celsius/mole)
m = molality of the solution (in moles of solute per kilogram of solvent)
i = van't Hoff factor (which represents the number of particles that the solute dissociates into when in solution)
First, you need to calculate the molality of the solution using the given mass of the solute and the mass of the solvent.
Molar mass of benzene (C6H6) = 78.11 g/mol
Mass of benzene solvent = 50.0 g
Mass of solute = 9.3 g
Moles of benzene solvent = Mass of benzene solvent / Molar mass of benzene
= 50.0 g / 78.11 g/mol
= 0.640 mol
Moles of solute = Mass of solute / Molar mass of solute
To find the moles of solute, we need to calculate the molality of the solution using the given mass of solute and solvent.
Molality (m) = moles of solute / mass of solvent (in kg)
Mass of solvent (benzene) = 50.0 g = 0.050 kg
Molality (m) = (9.3 g / Molar mass of solute) / 0.050 kg
To simplify the calculation, we can use the fact that the difference in boiling points is very small. We can assume that the molality of the solution is approximately equal to the molality of the solute.
ΔT = 81.19°C - 80.1°C = 1.09°C
Now, we can rearrange the formula to solve for the molar mass of the solute:
Molar mass of the solute = (ΔT / (Kbp * m)) * 1000
Molar mass of the solute = (1.09°C / (2.53 K/m * 0.050 mol/kg)) * 1000 = 432 g/mol
Therefore, the molar mass of the unknown solute is 432 g/mol.