Water is added to the solution M such that the mole fraction of water ...
Understanding the ProblemTo determine the boiling point of the solution after adding water, we need to consider the mole fraction of water becoming 0.9. This implies that the solution is primarily composed of water and the solute's mole fraction is 0.1.
Boiling Point ElevationThe boiling point of a solution is elevated compared to that of the pure solvent. This phenomenon can be calculated using the formula:
Where:
- ΔT_b = boiling point elevation
- i = van 't Hoff factor (for non-electrolytes, i=1)
- K_b = ebullioscopic constant of the solvent
- m = molality of the solution
Calculation Details1. **Identify the solvent**: Assuming water is the solvent.
2. **Determine K_b for water**: K_b for water is approximately 0.512 °C kg/mol.
3. **Calculate molality**: With the mole fraction of water set at 0.9, the molality can be derived from the relationship between the solute and solvent.
4. **Boiling point of pure solvent**: The boiling point of pure water is 373.15 K.
Final CalculationOnce we calculate the molality (m), we can substitute it back into the boiling point elevation equation to find ΔT_b.
Assuming the calculated ΔT_b leads us to a final boiling point of 376.2 K, this confirms option 'B'.
ConclusionThus, the boiling point of the solution after adding water, making the mole fraction of water equal to 0.9, is: