Ethylene glycol is used as an antifreeze in a cold climate. Mass of ethylene glycol which should be added to 4 kg of water to prevent it from freezing at – 6°C will be : (K_{f} for\; water=1.86 K\, kg\, mol^{-1},and\, molar\, mass\, of\, ethylene\, glycol=62\, g\, mol^{-1})

  • Option 1)

    804.32 g

  • Option 2)

    204.30 g

  • Option 3)

    400.00 g

  • Option 4)

    304.60 g

 

Answers (1)

As we learnt in

Mathematical Expression of Depression in Freezing point -

\Delta T_{f}= K_{f}\: m
 

- wherein

m = molarity of solvent 

K_{f} = cryoscopic  constant

    molal depress const

Units = \frac{K-K_{g}}{mole}

 

 \Delta T_{f}=K_{f}\times m

6=1.86\times\frac{Moles\ of\ solute}{4}

Moles of solute =\frac{6\times 4}{1.86}=12.9\ mole

Mass of solute  = Moles of solute \times Molar Mass

    =12.9\times 62=800

Correct option is 1.

 


Option 1)

804.32 g

This is the correct option.

Option 2)

204.30 g

This is an incorrect option.

Option 3)

400.00 g

This is an incorrect option.

Option 4)

304.60 g

This is an incorrect option.

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