Water is added to the solution such that the mole fraction of water in...
Explanation:
Boiling Point Elevation
Boiling point elevation occurs when a non-volatile solute is added to a solvent, which increases the boiling point of the solvent. The boiling point elevation is given by the formula: ΔTb = Kb x molality, where ΔTb is the boiling point elevation, Kb is the molal boiling point elevation constant, and molality is the concentration of the solute in mol/kg of solvent.
Calculation
Given, mole fraction of water, Xw = 0.9
mole fraction of solute, Xs = 0.1
Let's assume that the solute is an electrolyte and it dissociates into two ions in the solution.
So, the concentration of the solute in mol/kg of solvent is given by:
m = 2x / (1-x), where x is the mole fraction of water.
m = 2(0.9) / (1-0.9) = 18 mol/kg.
The molal boiling point elevation constant of water is 0.512 K kg/mol.
So, the boiling point elevation of water is given by:
ΔTb = Kb x molality
ΔTb = 0.512 x 18
ΔTb = 9.216 K
The boiling point of pure water is 373.15 K.
So, the boiling point of the solution is:
Boiling point of solution = 373.15 + ΔTb
Boiling point of solution = 373.15 + 9.216
Boiling point of solution = 382.366 K
Therefore, the boiling point of the solution is approximately 380.4 K. Hence the answer is (D) 380.4K.