Calculate the molecular mass of sulphur if 35.5 g of sulphure dissolves in 1 00 g of CS2 to produce a solution that has a boiling point of 49.48 c. Thanks to ur helps.
delta T = k*molality.
Solve for molality. You will need to know the boiling point of CS2 to obtain delta T.
m = moles/kg solvent
Solve for moles
moles = grams/molar mass
Solve for molar mass.
To calculate the molecular mass of sulfur, we need to use the concept of boiling-point elevation.
Boiling-point elevation is the phenomenon where the boiling point of a liquid increases when a non-volatile solute, such as sulfur, is dissolved in it. The change in boiling point is directly proportional to the molality of the solution.
First, we need to calculate the change in boiling point (∆Tb) by subtracting the boiling point of the pure solvent (CS2) from the boiling point of the solution:
∆Tb = Tbsolution - Tbpure solvent
Given that the boiling point of the solution is 49.48°C, we need to know the boiling point of pure CS2. The boiling point of CS2 is 46.25°C.
∆Tb = 49.48°C - 46.25°C
∆Tb = 3.23°C
The change in boiling point (∆Tb) is then used to calculate the molality (m) of the solution using the formula:
∆Tb = Kb × m
Kb refers to the molal boiling point elevation constant, which is specific to the solvent. For CS2, the Kb value is 2.53°C/m.
Plugging in the values:
3.23°C = 2.53°C/m × m
Simplifying the equation:
m² = 3.23/2.53
m² = 1.276
Taking the square root of both sides:
m = √1.276
m = 1.13 mol/kg
Now, we can calculate the number of moles of sulfur dissolved in the solution using the molality (m) and the mass of the solvent (CS2) given to us. The molar mass of CS2 is 76.14 g/mol.
Number of moles of sulfur = molality × mass of CS2 / molar mass of CS2
Number of moles of sulfur = 1.13 mol/kg × 100 g / 76.14 g/mol
Number of moles of sulfur = 1.48 mol
Finally, to find the molecular mass of sulfur, we divide the mass of sulfur (35.5 g) by the number of moles of sulfur (1.48 mol):
Molecular mass of sulfur = mass of sulfur / number of moles of sulfur
Molecular mass of sulfur = 35.5 g / 1.48 mol
Molecular mass of sulfur ≈ 24 g/mol
Therefore, the molecular mass of sulfur is approximately 24 g/mol.