Let mass of water initially present $=\mathrm{xg}$

Mass of sucrose $=(1000-\mathrm{x})\mathrm{g}$

Number of moles sucrose $=\frac{1000-\mathrm{x}}{342}$

Molality $\left(\mathrm{M}\right)=\frac{\frac{1000-\mathrm{x}}{342}}{\mathrm{x}/1000}=0.75$

$2565.5\mathrm{x}={10}^6-1000\mathrm{x}$

$\mathrm{x}=795.86 \mathrm{g}$

no. of moles of sucrose$=0.5969$

${\mathrm{\Delta T}}_{\mathrm{f}}={\mathrm{ik}}_{\mathrm{f}} \mathrm{m}$

$4=1\times 1.86\times \frac{0.5969}{(795.86-\mathrm{a})\mathrm{g}}\times 1000$

Ice separated$=518.3 \mathrm{g}$