شرح درس
Collective Properties of Solutions
CHEMISTRY - Secondary 1
In This part we will study
 Boiling point elevation:
When the vapor pressure of the liquid equals the atmospheric pressure, the liquid starts to boil and in this case the boiling point of the liquid is called the natural (normal) boiling point.
The natural (normal) boiling point : is the temperature at which the vapor pressure of the liquid equals the atmospheric pressure.
Measured boiling point : is the temperature at which the vapor pressure of the liquid equals the pressure exerted or acted on it.
* The boiling point can be used as an indicator for the purity of solvent, because the measured boiling point of the pure liquid equals its natural boiling point.

* When the pressure exerted on pure water or any other pure liquid is lower than the normal atmospheric pressure (1 atm), the measured boiling point becomes less than the natural boiling point.

*The boiling point of solution is always higher than the boiling point of pure solvent which forms it, because the vapor pressure of solution is lower than the vapor pressure of pure solvent which forms it, the solution needs more energy until its vapor pressure equals to the atmospheric pressure to boil.

* Boiling point elevation is directly proportional to the number of moles of ions or molecules of the solute in the solution.

Application :
Observe the opposite graph :
Pure water is boiled at 100°C at atmospheric pressure (1 atm). However, the addition of a certain quantity of salt in water raises the boiling point of the solution to T1

Notes
 The difference between the boiling point of the salty water and that of pure water.
Because adding salt to water decreases its vapor pressure, hence its boiling point becomes higher than that of pure water.

 The boiling point of an aqueous solution of sodium chloride is equal to the boiling point of an aqueous solution of potassium nitrate.

Because each of them produces the same number of moles of ions in the solution.

 The boiling point of an aqueous solution of sodium carbonate Na2CO3 is higher than the boiling point of an aqueous solution of the sodium chloride NaCl which has the same molal concentration.

Because the number of moles of ions dissolved in the solution of Na2CO3 is higher than that in the solution of NaCl and the boiling point increases by increasing the number of moles of ions dissolved in the solution.

Best wishes to you
Mr.Ahmed Elbasha

كيمياء الصف الاول الثانوي لغات - الفصل الدراسي الاول
شرح كيمياء لغات اولي ثانوي - مستر احمد الباشا
كيمياء لغات - الصف الاول الثانوي - كيمياء اولي ثانوي الترم الاول - كيمستري اولي ثانوي الترم الاول