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What mass of NaCI ("molar mass" =58.5g m...

What mass of `NaCI ("molar mass" =58.5g mol^(-1))` be dissolved in `65g` of water to tower the freezing point by `7.5^(@)C`? The freezing point depression constant, `K_(f)`, for water is `1.86 K kg mol^(-1)`. Assume van't Hoff factor for `NaCI` is `1.87`.

Text Solution

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Mass of the given solution is
`DeltaT_(f) = (ixx k_(f) xx W_(B) xx 1000)/(M_(B)xxW_(A))`
`WB = (DetlaT_(f) xx W_(A) xx M_(B))/(I xx kf xx 1000) = (7.5xx 58.5xx65)/(1.87 xx 1.86 xx 1000) = 8.199g`
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