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A solution containing 8 g of a substance...

A solution containing 8 g of a substance in 100 g of diethyl ether boils at `36.86^(@)C,` whereas pure ether boils at `35.60^(@)C.` Determine the molecular mass of the solute (For ether `K_(b)= 2.02 K kg mol ^(-1))`

Text Solution

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We have, mass of solute,` W_(2)=8g`
Mass of solvent, `W_(1) = 100 g `
Elevation of boiling point, `Delta T_(b) = 36.86 - 35.60=1.26 ^(@)C`
`K_(b)=2.02`
Molecular mass of the solute `M _(2) = ( 1000 xx W_(2) xx K _(b))/(Delta T_(b) xx W_(1))= (1000 xx 8 xx 2.02)/(1.26 xx 100) = (161.6)/(1.26)`
`= 128.25 g mol ^(-1).`
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