# Write the Formula to Determine the Molar Mass of a Solute Using Freezing Point Depresssion Method. - Chemistry

Numerical

Write the formula to determine the molar mass of a solute using freezing point depresssion method.

#### Solution

Depression of freezing point and molar mass of the solute:
When W2 gram of solute with molar mass M2 is dissolved in W1 gram of solvent, the molality m is given by

ΔT_f ∝ m

m="Mass of solute in kg"/("Molar mass of solue in kg "×" Mass of solvent in kg")

m=W_2/(M_2*W_1)

∴ The molar mass of a solute using freezing depression method is givenby,

ΔT_f ∝ m

ΔT_f = k_f . ("W"_2)/("M"_2) xx 1000/"W"_1
Where K_f - Cryoscopic constant
"W"_2 - mass of solute
"W"_1 - mass of solvent
"M"_2 - molecular mass of non-volatile solute

Concept: Colligative Properties and Determination of Molar Mass - Depression of Freezing Point
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