Question 13 Marks
What is Solubility? Explain Solubility of a solid in a liquid.
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Question 23 Marks
Explain vapour pressure of solutions of solids in liquids.
Question 33 Marks
Explain Van't Hoff factor.
Question 43 Marks
What is Isotonic, hypertonic and hypotonic Solution?
Question 53 Marks
Explain solubility of gas in a liquid solvent.
Question 63 Marks
What is azeotropes? Explain it's Types.
Answer
View full question & answer→→ "Some liquids on mixing, from azeotropes which are binary mixtures having the same composition in liquid and vapour phase and boil at a constant temperature."
→ In such cases, it is not possible to separate the components by fractional distillation.
→ There are two types of azeotropes
(1) Minimum boiling azeotrope :
→ "The solutions which show is large positive deviation from Raoult's law form minimum boiling azeotrope at a specific composition."
→ For example, ethanol-water mixture (obtained by fermentation of sugars) on fractional distillation gives a solution containing approximately 95% by volume of ethanol. Once this composition, known as azeotrope composition, has been achieved, the liquid and vapour have the same composition, and no further separation occurs.
(2) Maximum boiling azeotrope:
→ "The solutions that show large negative deviation from Raoult's law form maximum boiling azeotrope at a specific composition."
→ Nitric acid and water is an example of this class of azeotrope. This azeotrope has the approximate composition, 68% nitric acid and 32% water by mass, with a boiling point of 393.5 K
→ In such cases, it is not possible to separate the components by fractional distillation.
→ There are two types of azeotropes
(1) Minimum boiling azeotrope :
→ "The solutions which show is large positive deviation from Raoult's law form minimum boiling azeotrope at a specific composition."
→ For example, ethanol-water mixture (obtained by fermentation of sugars) on fractional distillation gives a solution containing approximately 95% by volume of ethanol. Once this composition, known as azeotrope composition, has been achieved, the liquid and vapour have the same composition, and no further separation occurs.
(2) Maximum boiling azeotrope:
→ "The solutions that show large negative deviation from Raoult's law form maximum boiling azeotrope at a specific composition."
→ Nitric acid and water is an example of this class of azeotrope. This azeotrope has the approximate composition, 68% nitric acid and 32% water by mass, with a boiling point of 393.5 K
Question 73 Marks
Explain abnormal molar Tasses. Also explain association and dissociation of Solute.
Answer
View full question & answer→→ Ionic compounds when dissolved in water dissociate into cations and anions.
→ For example, if we dissolve one mole of KCI (74.5 g) in water, we expect one mole each of K+ and Cl- ions to be released in the solution. If this happens, there would be two moles of particles in the solution.
→ one mole of KCl in one kg of water would be expected to increase the boiling point by 2 x 0.52 K = 1.04 Κ
→ If we did not know about the degree of dissociation, we could be led to conclude that the mass of 2 mol particles is 74.5 g and the mass of one mole of KCl would be 37.25 g.
→ When there is dissociation of solute into ions, the experimentally determined molar mass is always lower than the true value.
→ Molecules of ethanoic acid (acetic acid) dimerise in benzene due to hydrogen bonding. This normally happens in solvents of low dielectric constant. In this case the number of particles is reduced due to dimerisation.
→ It can be undoubtedly stated here that if all the molecules of ethanoic acid associate in benzene, then $\Delta T _{ b }$ or $\Delta T _{ f }$ for ethanoic acid will be half of the normal value.
→The molar mass calculated on the basis of this $\Delta T_b$ or $\Delta T_f$ will, therefore, be twice the expected value. Such a molar mass that is either lower or higher than the expected or normal value is called as abnormal molar mass.
→ For example, if we dissolve one mole of KCI (74.5 g) in water, we expect one mole each of K+ and Cl- ions to be released in the solution. If this happens, there would be two moles of particles in the solution.
→ one mole of KCl in one kg of water would be expected to increase the boiling point by 2 x 0.52 K = 1.04 Κ
→ If we did not know about the degree of dissociation, we could be led to conclude that the mass of 2 mol particles is 74.5 g and the mass of one mole of KCl would be 37.25 g.
→ When there is dissociation of solute into ions, the experimentally determined molar mass is always lower than the true value.
→ Molecules of ethanoic acid (acetic acid) dimerise in benzene due to hydrogen bonding. This normally happens in solvents of low dielectric constant. In this case the number of particles is reduced due to dimerisation.
→ It can be undoubtedly stated here that if all the molecules of ethanoic acid associate in benzene, then $\Delta T _{ b }$ or $\Delta T _{ f }$ for ethanoic acid will be half of the normal value.
→The molar mass calculated on the basis of this $\Delta T_b$ or $\Delta T_f$ will, therefore, be twice the expected value. Such a molar mass that is either lower or higher than the expected or normal value is called as abnormal molar mass.
Question 83 Marks
What is ideal Solution? Explain with examples.
Answer
View full question & answer→→ "The solutions which follows Raoult's law over the entire range of concentration are known as ideal solutions."
→ The enthalpy of mixing of the pure components to form the solution is zero and the volume of mixing is also zero,
$\Delta_{\text {mix }} H =0 \quad \Delta_{\text {mix }} V =0$
→ It means that no heat is absorbed or evolved when the components are mixed.
→ The volume of solution would be equal to the sum of volumes of the two components.
→ At molecular level, ideal behaviour of the solutions can be explained by considering two components A and B. In pure components, the intermolecular attractive interactions will be of types A-A and B-B, where as in the binary solutions in addition to these two interactions, A-B type of interactions will also be present.
→ If the intermolecular attractive forces between the A-A and B-B are nearly equal to those between A-B, this leads to the formation of ideal solution.
→ Example of ideal solution:
→ n-hexane and n-heptane, bromoethane and chloroethane, benzene and toluene, etc.
→ The enthalpy of mixing of the pure components to form the solution is zero and the volume of mixing is also zero,
$\Delta_{\text {mix }} H =0 \quad \Delta_{\text {mix }} V =0$
→ It means that no heat is absorbed or evolved when the components are mixed.
→ The volume of solution would be equal to the sum of volumes of the two components.
→ At molecular level, ideal behaviour of the solutions can be explained by considering two components A and B. In pure components, the intermolecular attractive interactions will be of types A-A and B-B, where as in the binary solutions in addition to these two interactions, A-B type of interactions will also be present.
→ If the intermolecular attractive forces between the A-A and B-B are nearly equal to those between A-B, this leads to the formation of ideal solution.
→ Example of ideal solution:
→ n-hexane and n-heptane, bromoethane and chloroethane, benzene and toluene, etc.