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A solution containing 2.56 g of sulphur dissolved in 100 g of naphthalene whose melting point is 80^(@)1C gave a freezing point lowering of 0.680^(@)C. Calculate the formula of sulphur (K_(f) for naphthalene = 6.8 K/m) |
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Answer» Solution :`w_(2)="2.56 G,"w_(1)="100 g ,"K_(f)="6.8 Km"^(-1), DeltaT_(f)=0.68^(@)C` `"Now,"M_(2)=(1000K_(f)w_(2))/(w_(1)xxDeltaT_(f))` Substituting the value of `K_(f), w_(2), w_(1) and DeltaT_(f), M_(2)=("1000 g KG"^(-1)xx"6.8 K kg mol"^(-1)xx"2.56 g")/("100 g "xx"0.68 K")="256 g mol"^(-1)` LET molecular formula of sulphur be `S_(x)" ,"` Atomic mass of sulphur = 32 Molecular mass of `S_(x)=x xx 32""therefore""x xx32=256"or"x=(256)/(32)=8` Therefore, the molecular formula of sulphur is `S_(8).` |
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