The correct option is
B 376.2 K
The expression for the elevation in the boiling point of the solution is ΔTb=Kb×m......(i)
Here, ΔTb is the elevation in the boiling point, Kb is the boiling point elevation constant of water
and m is the molality of the solution.
The mole fraction of water is 0.9 and the mole fraction of ethanol is 0.1
Thus water acts as a solvent.
The molality of a solution is the number of moles of ethanol (solute) present in 1 kg of water (solvent).
Molar mass of water = 18 gram/mole.
Hence, the molality of the solution is
m=0.10.9×18×1000 m
Substitute values in equation (i)
The elevation in boiling point is ΔTb=0.52×0.10.9×18×1000=3.2K
The boiling point of pure water is 373 K.
Boiling point of solution =373+3.2=376.2K