Calculate the normal freezing point of a 0.7439 mol aqueous solution of c12h22o11 that has a density of 1.35g/ml. The molal freezing point depression constant of water is 1.86 kg/mole

Respuesta :

Answer:

Freezing point of solution = -2.740C

Explanation:

The solution is attached herewith

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The normal freezing point of an aqueous solution of C₁₂H₂₂O₁₁ is -1.26°C

The freezing point depression can be calculated using the formula:

ΔTf = i* Kf*m ; where

  • i = van’t Hoff factor
  • Kf = freezing point depression constant
  • m = molalility of solution

The molality of the aqueous solution of C₁₂H₂₂O₁₁ is first determined using the formula:

  • molality = moles of solute/mass of water in kg

The mass of water is unknown but is determined from the mass of the solute and solution from the formula:

  • mass of solvent (water) = mass of solution - mass of solute

mass of solute = number of moles * molar mass

moles of solute in 1 L solution = 0.7439 moles

molar mass of solute, C₁₂H₂₂O₁₁ = 342.0 g/mol

mass of solute = 0.7439 moles * 342.0 g

mass of solute = 254.41 g

mass of solution = density * volume

volume of solution = 1 L = 1000 mL

mass of solution = 1.35g/ml * 1000 mL

mass of solution = 1350 g

Therefore, mass of solvent (water) = 1350 g - 254.41 g

mass of solvent (water) = 1095.59 g

mass of solvent (water) in kg = 1095.59 g * 1 kg/ 1000 g

mass of solvent (water) in kg = 1.0956Kg

Thus, molality of solution = 0.7439 moles / 1.0956 Kg

molality of solution = 0.679 mol/kg

The freezing point depression, ΔTf, is then determined using the formula: ΔTf = i* Kf*m

Since C₁₂H₂₂O₁₁ is a non-electrolyte; i for C₁₂H₂₂O₁₁ = 1

Kf of water = 1.86 kg/mole

m = 0.679 mol/kg

ΔTf = 1 * 1.86 * 0.679

ΔTf = 1.26 °C

Therefore, freezing point depression, ΔTf = 1.26 °C

normal freezing point of solution = freezing point of water - freezing point depression

normal freezing point of solution = 0.0°C - 1.26°C

normal freezing point of solution = -1.26°C

Therefore, the normal freezing point of an aqueous solution of C₁₂H₂₂O₁₁ is -1.26°C

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