Answer:
S₁₂
Explanation:
The freezing point depression (ΔTf) is a colligative property that can be calculated using the following expression.
ΔTf = Kf × m
where,
Kf: freezing point depression
m: molality
ΔTf = Kf × m
m = ΔTf / Kf
m = 0.156 °C / (29.8 °C/m)
m = 5.23 × 10⁻³ m
The molality is:
m = moles of solute / kilograms of solvent
moles of solute = m × kilograms of solvent
moles of solute = 5.23 × 10⁻³ mol/kg × 0.5000 kg
moles of solute = 2.62 × 10⁻³ mol
1.00 g corresponds to 2.62 × 10⁻³ moles. The molar mass of Sₙ is:
1.00 g/2.62 × 10⁻³ mol = 382 g/mol
We can calculate n.
n = molar mass of Sₙ / molar mass of S
n = (382 g/mol) / (32.0 g/mol)
n = 11.9 ≈ 12
The molar formula is S₁₂.
