If Sodium nitrate is completely dissociated into cations and anions in aqueous solution, the change…

If Sodium nitrate is completely dissociated into cations and anions in aqueous solution, the change in freezing point of water ($\Delta T_f$), when $0.05\text{ mol}$ of sodium nitrate is dissolved in $1\text{ kg}$ of water is: ($K_f = 1.86\text{ K kg mol}^{-1}$)