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A solution containing 0.2563g of naphthalene (molecular mass = 128) in 50g of carbon tetrachloride yields a boiling point elevation of `0.201^(@)C` while a solution of 0.6216g of an unknown solute in the same mass of the solvent gives a boiling point elevation of `0.647^(@)C`. Find the molecular mass of the unknown solute. |
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Answer» We know that, `K_(b)=(DeltaT_(b)xxWxxm)/(1000xxw)` For `C Cl_(4),K_(b)=(0.201xx50xx128)/(1000xx0.2563)=5.019` `K_(b)` is now used in the second part of the problem `m=(1000xxK_(b)xxw)/(DeltaT_(b)xxW)` `=(1000xx5.019xx0.6216)/(0.647xx50)=96.44`. |
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