The boiling point of water H 2 O is 100.0 °C at 1 atmosphere. A nonvolatile, non

Question

The boiling point of water H2O is 100.0°C at 1 atmosphere. A nonvolatile, nonelectrolyte that dissolves in water is antifreeze (ethylene glycol).

How many grams of antifreeze, CH2OHCH2OH (62.10 g/mol), must be dissolved in 209.0 grams of water to raise the boiling point by 0.500 °C ?

g antifreeze???

The freezing point of water H2O is 0.00°C at 1 atmosphere. A nonvolatile, nonelectrolyte that dissolves in water is urea .

How many grams of urea, CH4N2O (60.10 g/mol), must be dissolved in 261.0 grams of water to reduce the freezing point by 0.300°C ?

g urea.

Explanation / Answer

1. DTb = i*Kb*m

i = vanthoff factor of ethyleneglycol = 1

Kb of water = 0.512 c*kg/mol

m = molality of solution = (wt of solute/Mwt)*(1000/wt of solvent in grams)

   = (w/62.1)*(1000/209)

DTb = 0.5 c

0.5 = 1*0.512*(w/62.1)*(1000/209)

w = wt of antifreeze, CH2OHCH2OH = 12.67 grams

2.

DTf = i*Kf*m

i = vanthoff factor of urea = 1

Kf of water = 1.86 c*kg/mol

m = molality of solution = (wt of solute/Mwt)*(1000/wt of solvent in grams)

   = (w/60.1)*(1000/261)

DTf = 0.3 c

0.3 = 1*1.86*(w/60.1)*(1000/261)

w = wt of urea, CH4N2O = 2.53 grams

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