Freezing point depression of a solution is given by,
△Tf=i×Kf×m
where,
△Tf is the depression in freezing point.
Kf is molal depression constant.
m is molality of solution.
Van't hoff factor, i=1 for glucose)
Molality (m)=wsoluteM×1000Wsolvent
where,
w is weight of solute
W is weight of solvent
M is molar mass of the solute
ΔTf=1×1.86×40×1000180×200 (Mass of water=200 gas d=1 g/mL)
=2.06
∴ Freezing point =To−ΔTf
To is freezing point of water
=273.15−2.06
=271.09 K
=271 K