1.

1Kg of an aqueous solution of Sucrose is cooled and maintained at `-4^(@)"C".` How much ice will be seperated out if the molality of the solution is 0.75? `"K"_("F")("H"_(2)"O")=1.86"Kg mol"^(-1)"K"`

Answer» Since molality of solution is .75,
hence.75 moles of sucrose are present in 1000g of solvent(i.e. water)
`therefore"m"_("solution")="m"_("water")+"m"_("sucrose")=1000+.75xx342=1256.5"gm"`
`therefore"m"_("sucrose")("in kg")=256.5/1256.5xx1000=204.14"gm",."m"_("water")=1000-204.14=795.86"gm"`
`therefore Delta "T"_("F")="K"_("F")xx"m"implies4=1.86xx(204.14//342)/("W"//1000)implies"w"=277.15`
`therefore "amount of ice =795.86-277.15=518.31 gm"`


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