Question

In order to depress the freezing point of water to -12°C, how much magnesium nitrate would you have to add to 500g of water?

Answer 1

$∆T_f=T_i-T_{fsol}$

$∆T_f=0--12=12°c$

The cryoscopic constant of water is equal to $1.86°C$ $kg/mol^{-1}$

van't Hoff factor, of magnesium nitrate is $2$

$Molarity =\frac{12}{2×1.86}=3.23 mol/kg$