Elevation in boiling point:
- Boiling point elevation refers to the increase in the boiling point of a solvent upon the addition of a solute.
- When a non-volatile solute is added to a solvent, the resulting solution has a higher boiling point than that of the pure solvent.
- For example, the boiling point of a solution of sodium chloride (salt) and water is greater than that of pure water.
- The boiling point of a liquid is the temperature at which its vapor pressure is equal to the pressure of its surrounding environment.
- Non-volatile substances do not readily undergo evaporation and have very low vapor pressures (assumed to be zero).
- When a non-volatile solute is added to a solvent, the vapor pressure of the resulting solution is lower than that of the pure solvent.
The boiling point of a solution containing a non-volatile solute can be expressed as follows:
The boiling point of solution = boiling point of pure solvent + boiling point elevation ().
The elevation in boiling point () is proportional to the concentration of the solute in the solution. It can be calculated via the following equation.
Where,
- is the Van't Hoff factor
- is the ebullioscopic constant
- is the molality of the solute
Calculate the value of -
The molarity of the aqueous solution of is .
And of is ,
The expression used for the calculation of Vant Hoff's factor ,
The factor is given below:
To calculate the value of the following reaction is used:
Hence, the elevation of the boiling point of aqueous solution is two times that of aqueous solution. The value of x is 5.