1.

`15.0 g` of an unknown molecular material was dissolved in `450 g` of water. The reusulting solution was found to freeze at `-0.34 .^(@)C`. What is the the molar mass of this material. (`K_(f)` for water `= 1.86 K kg mol^(-1)`)

Answer» `W_(A) = 15.0 gm`
`W_(B) = 450 gm`
`KF_(2) = 1.86 K kg//"mol"`
For water,
` DeltaT_(f) = K_(f) xx "molality"`
`0 - (0.34) = 1.86 K kg mol^(-1) xx (15 g xx 1000)/(M xx 450)`
`M = (1.86 K kg mol^(-1) xx 15 gm xx 1000)/(0.34 K xx 450 kg) = 182.35 gm//mol`.


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