$\Rightarrow \text { Mass of sucrose }=(1000-{x})\, {gm}$

$\Rightarrow \text { moles of sucrose }=\left(\frac{1000-{x}}{342}\right)$

$\Rightarrow 0.75=\frac{\left(\frac{1000-{x}}{342}\right)}{\left(\frac{{x}}{1000}\right)} \Rightarrow \frac{{x}}{1000}=\frac{1000-{x}}{342 \times 0.75}$

$\Rightarrow 256.5 {x}=10^{6}-1000 {x}$

$\Rightarrow {x}=795.86\, {gm}$

$\Rightarrow \text { moles of sucrose }=0.5969$

New mass of ${H}_{2} {O}={a}\, {kg}$

$\Rightarrow 4=\frac{0.5969}{{a}} \times 1.86 \Rightarrow {a}=0.2775\, {~kg}$

$\Rightarrow \text { ice separated }=(795.86-277.5)=518.3 \,{gm}$