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Boiling point of water at 750 mm Hg is 99.63^(@)C. How much sucrose is to be added to 500 g of water such that it boils at 100^(@)C? Molal elevation constant for water is "0.52 K kg mol"^(-1). |
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Answer» Solution :Elevation in boiling point required `(DeltaT_(b))=100-99.63^(@)=0.37^(@)` Mass of solvent (water), `w_(1)=500g` `"Molar mass of solvent, "M_(1)="18 g mol"^(-1),"Molar mass of solute, "C_(12)H_(22)O_(11)="342 g mol"^(-1)` `"Applying the formula, "M_(2)=(1000K_(b)w_(2))/(w_(1)DeltaT_(b))` `"or"w_(2)=(M_(2)xxw_(1)xxDeltaT_(b))/(1000xxK_(b))=("342 g mol"^(-1)xx500 g xx0.37K)/("1000 g kg"^(-1)xx0.52"K kg mol"^(-1))=121.7g.` |
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