If 0.48 g of sulfur are added to 200 g of carbon tetracholoride, and the freezing point of the carbon tetrachloride (Kf=30 degrees C/m) is depressed by 0.28 degrees C, what is the molar mass and molecular formula of the sulfur?
.48g * 1mol/32.07g= .01497 mol S
.01497/.2 kg = .07485 molality
273.28K= i * 293K * .07485
i = .08
??
.28C = 30C * x/.2kg
x = .001867 moles S
.001867 moles S = .48g S/x
x = 8.0177 molecular formula for S
Is this correct?
To find the molar mass and molecular formula of sulfur, we need to use the freezing-point depression equation and the formula for calculating molarity and molality.
The freezing-point depression equation is:
ΔT = Kf * m * i
Where:
ΔT is the change in freezing point (0.28°C in this case)
Kf is the freezing-point depression constant for the solvent (30°C/m in this case)
m is the molality of the solution (0.07485 mol/kg in this case)
i is the van't Hoff factor (unknown)
Rearranging the equation, we get:
i = ΔT / (Kf * m)
Substituting the given values, we have:
i = 0.28°C / (30°C/m * 0.07485 mol/kg)
i ≈ 0.118
The van't Hoff factor (i) represents the number of particles formed in the solution when the substance dissolves. For ionic compounds, the i value is equal to the number of ions released, but for molecular compounds like sulfur, the i value is often considered equal to 1.
Now, to find the molar mass of sulfur, we can use the molality formula:
m = moles of solute / mass of solvent (in kg)
We are given:
moles of solute = 0.01497 mol
mass of solvent = 0.2 kg
Rearranging the formula and solving for molar mass (M), we get:
M = moles of solute / molality
M = 0.01497 mol / 0.07485 mol/kg
M ≈ 0.2 kg/mol
The molar mass obtained is in kg/mol, so we need to convert it to g/mol:
0.2 kg/mol * 1000 g/kg ≈ 200 g/mol
The molar mass of sulfur is approximately 200 g/mol.
To find the molecular formula of sulfur, we need to divide the molar mass of sulfur (200 g/mol) by the atomic mass of sulfur (32.07 g/mol):
200 g/mol / 32.07 g/mol ≈ 6.23
The result is approximately 6.23, which suggests that the molecular formula of sulfur could be S6. However, it is important to note that sulfur exists as S8 in its elemental form, so the molecular formula of sulfur is likely S8.
In conclusion, the molar mass of sulfur is approximately 200 g/mol, and its molecular formula is likely S8.
You aren't on the right track.
delta T = Kf*m
Solve for m
m = moles S/kg solvent
Solve for moles S.
moles S = grams S/molar mass SSolve for molar mass S.
part 2:
(molar mass S/32.066) = x
molecular formula = Sx