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Boiling point of water at 750 mm Hg is 99.63^(@)C. How 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 :Here, elevation of boiling POINT `DELTA T_(b)=(100+273)-(99.63+273)=0.37 K` Mass of water, `w_(1)=500 g` Molar mass of sucrose `(C_(12)H_(22)O_(11))`, `M_(2)=11xx12+22xx1+11xx16=34 g mol^(-1)` Molal elevation constant, `K_(b)=0.52 " K KG mol"^(-1)` We know that : `Delta T_(f)=(K_(b)xx1000xx w_(2))/(M_(2)xx w_(1))` `w_(2)=(Delta T_(b)xx M_(2)xx w_(1))/(K_(b)xx1000)=(0.37xx342xx500)/(0.52xx1000)` = 121.7 (approximately) HENCE, 121.67 g of sucrose is to be added. |
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