Why does a solution containing non-volatile solute have higher boiling point than the pure solvent Class 12?

Why does a solution containing non-volatile solute have higher boiling point then the pure solute.why it the evolution of boiling point a colligative properties.

Posted by Prashant Gandhi 3 years, 7 months ago

The boiling point of substance can be defined as, it is the temperature at which the vapour pressure of the substance equal to atmospheric pressure. According to Raoult's law, the vapour pressure of a solvent decreases in the presence of a non-volatile solute. Thus, the vapour pressure of a solution containing a non-volatile solute requires a high temperature to become equal to the atmospheric pressure. That is why the boiling point of a solution containing a non-volatile solute increases. Thus, the solution containing a non-volatile solute has a higher boiling point than a pure solvent. Example of non-volatile solute sugar, NaCl. etc.

Why does a solution containing non-volatile solute have higher boiling point than the pure solvent ?

Boiling point is the temperature at which the vapour pressure of a substance becomes equal to the atmospheric pressure. According to Raoult's law, the vapour pressure of a solvent decreases in the presence of a non-volatile solute. Thus, the vapour pressure of a solution containing a non-volatile solute requires a high temperature to become equal to the atmospheric pressure. That is why the boiling point of a solution containing a non-volatile solute increases. Thus, the solution containing a non-volatile solute has a higher boiling point than a pure solvent.

Concept: Vapour Pressure of Liquid - Vapour Pressure of Liquid- Liquid Solutions

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14.

Give reasons for the following:
(i) N2 is less reactive at room temperature.

(ii) H2Te is the strongest reducing agent amongst all the hydrides of Group 16 elements.

(iii) Helium is used in diving apparatus as a diluent for oxygen.

Two nitrogen atoms are joined by triple bonds. The nitrogen atom is very small, therefore the bond length is also quite small (109.8pm) and as the result, the bond dissociation energy is quite high (946Kj/mol) Therefore, N2 is less reactive at room temperature.

H2Te is the strongest reducing agent among the hydrides of group 16. The size of Te is very large due to which the bonding between hydrogen and Te is not strong. On the other hand, the electronegativity of Te is very less. So it will easily loose hydrogen. As the size of the elements increases in the order O < S < Se < Te, thus bond strength decreases from H2O to H2Te and therefore, the bond dissociation enthalpy decreases.  Hence, due to the increase in the tendency to release proton, the element's reducing tendency also increases.

(iii) Helium is used in diving apparatus as a diluent for oxygen because it is chemically inert and does not participate in the chemical reaction. Helium has low solubility in water than many other gases, such as nitrogen. Due to low solubility means it does not enter the bloodstream, even under pressure commonly experienced by deep sea divers.