Question

some ethylene glycol is added to your car's cooling system along with 5.0 kg. of water. If the freezing point of the water glycol solution is -15.0 degree celsius what mass of HOCH2CH2OH must have been added?

Answer 1

Taking K_f of water as $=1.86K\>kgmol^{-1}$

$-\Delta\>T_f=K_f×M$

$0-(-15)=1.86×M$

$M=\frac{15}{1.86}=8.0645\>moles$

Molar mass of ethylene glycol

= 62g

Mass added in 5kg of water

=8.0645×62×5

=2499.995g

=2.5kg