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What mass of NaCl must be dissolved in 65.0 g of water for lowering the freezing point of water by 7.50^(@)C ? The freezing point depression constant (K_(f)) for water is 1.86^(@) C/m. Assume Van't Hoff factor for NaCL is 1.87 (molar mass of NaCl = 58.5 g )

Answer»

SOLUTION :`W_(B)= ?, M_(B) = 58.5 , W_(A) = 65 ` g
`DELTA T_(f) = 7.5`
`K_(f) = 1.86`

i=1.87
`Delta T_(f) = iK_(f)` m
7.5 = 1.87 `xx 1.86 xx (W_(B))/(58.5) xx (1000)/(65)`
28518.7= 3478.2 `W_(B)`
`W_(B) = ` 8.19


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