Depression of the Freezing Point
In chemistry we assume a mixture of two solids as two different phases, which do not interfere with each other and thus, the solid solute in the solid mixture will not interfere with the solid solvent. So, the vapour pressure of the solid solution and solid solvent will always be same. In a similar way, when two immiscible liquids are mixed together, the total vapour pressure is counted as the sum of Vapour pressures of the liquids if kept separately.
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