First Year Chemistry Chapter 9 Online Short Questions for 1st Year Chemistry Chapter 9 Solutions Preparation

What is critical solution temperature? Give the critical solution temperature of phenol water system?

• Ans 1: Critical Temperature: The temperature at which two conjugate solutions merge into each other to form homogeneous mixture is called critical solution temperature or consulate temperature.
  Phenol-Water system has critical temperature of 65.9°C at which two conjugate solution merge into one another.

Why hydration energy of Na⁺ Ion is less than Li⁺ Ion?

• Ans 1: Hydration energy of an ion depends upon two parameters .
  1. Ionic Radii
  2. Charge density

  Greater the ionic radii of monopositive ions, smaller is the heat of hydration and vice versa. Hence Na⁺ Has greater size than Li⁺ That's why its heat of hydration is low.

Define molal freezing point constant giving example.

• Ans 1: It is depression of freezing point, when one mole of non-volatile and non-electrolyte solute is dissolved in one kg of solvent.

What are the names major parts of apparatus used in Landsberger's method for elevation of boiling point?

• Ans 1:
  1. An inner tube with a hole in its side.This tube is graduated.
  2. A boiling flask which send the solvent vapours into the graduated tube through a rosehead..
  3. An outer tube, which receives hot solvent vapours coming from the side hole of the inner tube.
  4. A thermometer which can read up to 0.01K.

Differentiate between continuous and discontinuous solubility curves?

• Ans 1: Continuous Solubility Curve: These are smooth curves and do not show any sharp break points.(Continuous increase or decreases in solubility with temperature.e.g.Solubility curves of KCIO₃,K₂Cr₂O₇ Etc.
  Discontinuous Solubility Curves: These are not smooth and shows sudden breaks due to sudden changes in solubilities.e.g.Solubility curves of Na₂SO₄,CaCl_{2 etc.}

Define fractional crystallization.How is it useful?

• Ans 1: Fractional Crystallization: The separation of solid substances from a solution one by one on cooling is called fractional crystallization.This technique is used for separation of impurities from sample.

Boiling points of liquid are increased when solute is added to them.Give reason?

• Ans 1: Because the vapour pressure of solvent decrease due to the pressure of solute.Therefore,we have to supply high temperature in order to equalized the vapour pressure of solvent to external pressure to boil it. This results in the increase of boiling point of solvent in the presence of solute.

Fractional crystallization technique is used to purify the chemical products.Justify?

• Ans 1: The separation of solid substance from a solution one by one on cooling is called fractional crystallization.Solubilities depends upon temperature.
  E.g.Solubility of KNO₃ Rapidly changes with temperature but solubility of KCI and Kbr changes gradually.Thus one substance may precipitate earlier by cooling, leaving behind others.

• Ans 1:

Differentiate between zeotropic and azeotropic mixture?

• Ans 1: Zeotropic Mixtures: The liquid mixtures which distills with change in composition is called zeotropic mixtures,e.g.Methyl Alcohol-water solution.
  Azeotropic Mixtures: The liquid mixtures which boil at constant temperature and distill over without changes in composition like a pure compound at any temperature is called azeotropic mixtures.eg, HCI formsazeotropic with water.

Fractional crystallization technique is used to purify the chemical products.Justify?

• Ans 1: The separation of solid substance from a solution one by one on cooling is called fractional crystallization.Solubilities depends upon temperature.
  E.g.Solubility of KNO₃ Rapidly changes with temperature but solubility of KCI and Kbr changes gradually.Thus one substance may precipitate earlier by cooling, leaving behind others.

What is critical solution temperature? Give the critical solution temperature of phenol water system?

• Ans 1: Critical Temperature: The temperature at which two conjugate solutions merge into each other to form homogeneous mixture is called critical solution temperature or consulate temperature.
  Phenol-Water system has critical temperature of 65.9°C at which two conjugate solution merge into one another.

State ebullioscopeic constant and cryoscopic constant?

• Ans 1: Ebullioscopic constant: It is elevation in boiling point which is produced,when 1 mole of solute is dissolved in 1 kg of solvent.It is denoted by K_b. Its value is 0.52C° for water.
  Cryoscopic constant: It is depression in freezing point which is produced when q mole of solute is dissolved in 1 kg of solvent. It is denoted by K_f
  Its value is 1.86 C° for water
  

Colligative properties are obeyed when the solute is non-electrolyte and also when the solutions are dilute.Explain?

• Ans 1: Colligative properties depend upon number of solute, particles in solution of non-electrolyte. Solute do not ionize in solution and its number of particles remain same. E.g1 mole of urea produces 3.02x10²³ Particles in solution.When solution is dilute, less number of solute particles far away from each other and they behave independently and colligative properties are obeyed.

Differentiate between zeotropic and azeotropic mixture?

• Ans 1: Zeotropic Mixtures: The liquid mixtures which distills with change in composition is called zeotropic mixtures,e.g.Methyl Alcohol-water solution.
  Azeotropic Mixtures: The liquid mixtures which boil at constant temperature and distill over without changes in composition like a pure compound at any temperature is called azeotropic mixtures.eg, HCI formsazeotropic with water.

Why is the vapour pressure of a solution less than pure solvent?

• Ans 1: In pure solvent all the surface of solvent is covered by solvent molecules.But when a solute is added to it from a solution.Some surface is occupied by solute particles. Hence escaping tendency of solvent is decreases and thus vapour pressure of solution also lowered.

Why the non-ideal solutions do not obey the Raoult's law?

• Ans 1: Mnay solutions do not behave ideally as they show deviation from Raoult's law due to difference in their molecular structure I.e. Size, shape and intermolecular forces.During their formation change in volume and enthalpy take place.Hence they show deviation from ideality.

Differentiate between continuous and discontinuous solubility curves?

• Ans 1: Continuous Solubility Curve: These are smooth curves and do not show any sharp break points.(Continuous increase or decreases in solubility with temperature.e.g.Solubility curves of KCIO₃,K₂Cr₂O₇ Etc.
  Discontinuous Solubility Curves: These are not smooth and shows sudden breaks due to sudden changes in solubilities.e.g.Solubility curves of Na₂SO₄,CaCl_{2 etc.}

Give the condition of colligative properties?

• Ans 1: There are following conditions for colligative properties:
  1. Solution must be dilute.
  2. Solute must be non-volatile.
  3. Solute must be non-electrolyte.

Why hydration energy of Na⁺ Ion is less than Li⁺ Ion?

• Ans 1: Hydration energy of an ion depends upon two parameters .
  1. Ionic Radii
  2. Charge density

  Greater the ionic radii of monopositive ions, smaller is the heat of hydration and vice versa. Hence Na⁺ Has greater size than Li⁺ That's why its heat of hydration is low.

Why is the vapour pressure of a solution less than pure solvent?

• Ans 1: In pure solvent all the surface of solvent is covered by solvent molecules.But when a solute is added to it from a solution.Some surface is occupied by solute particles. Hence escaping tendency of solvent is decreases and thus vapour pressure of solution also lowered.

Colligative properties are obeyed when the solute is non-electrolyte and also when the solutions are dilute.Explain?

• Ans 1: Colligative properties depend upon number of solute, particles in solution of non-electrolyte. Solute do not ionize in solution and its number of particles remain same. E.g1 mole of urea produces 3.02x10²³ Particles in solution.When solution is dilute, less number of solute particles far away from each other and they behave independently and colligative properties are obeyed.

Define "heat of solution" and "hydration energy"?

• Ans 1: The quantity of heat energy that is absorbed or released when a substance forms solution, is termed as heat of solution.
  When ionic compound is dissolved in water, the first step is the separation of ions from solid and second step is separated ions are surrounded by solvent molecules.A Hydrated ion is attracted by the solvent dipoles and energy is released, so second step is exothermic. The energy given out by the second step is known as the hydration energy .

State ebullioscopeic constant and cryoscopic constant?

• Ans 1: Ebullioscopic constant: It is elevation in boiling point which is produced,when 1 mole of solute is dissolved in 1 kg of solvent.It is denoted by K_b. Its value is 0.52C° for water.
  Cryoscopic constant: It is depression in freezing point which is produced when q mole of solute is dissolved in 1 kg of solvent. It is denoted by K_f
  Its value is 1.86 C° for water
  

Why hydration energy of Na⁺ Ion is less than Li⁺ Ion?

• Ans 1: Hydration energy of an ion depends upon two parameters .
  1. Ionic Radii
  2. Charge density

  Greater the ionic radii of monopositive ions, smaller is the heat of hydration and vice versa. Hence Na⁺ Has greater size than Li⁺ That's why its heat of hydration is low.

• Ans 1:

One molal solution of urea is more dilute as compared to its one molar solution.Why?

• Ans 1: One molal solution contains one mole of urea per kg of solvent, while one mole solution contains one mole of urea per one dm³ Of solution.In one molal solution amount of water is greater than one molar solution because amount of solution included in it.

Give the condition of colligative properties?

• Ans 1: There are following conditions for colligative properties:
  1. Solution must be dilute.
  2. Solute must be non-volatile.
  3. Solute must be non-electrolyte.

Define fractional crystallization.How is it useful?

• Ans 1: Fractional Crystallization: The separation of solid substances from a solution one by one on cooling is called fractional crystallization.This technique is used for separation of impurities from sample.

Define solubility giving one example?

• Ans 1: The solubility is defined as the concentration of the solute in the solution when it is in equilibrium with the solid substance at a particular temperature. Solubility is expressed in terms of number of grams of solute in 100g of solvent. At a particular temperature, saturated solution of NaCl in water at O° C contains 37.5g NaCl in 100g of water.

Give two examples of liquid solution?

• Ans 1:
  1. Alcohol in water
  2. Benzene in toluene

Define solubility giving one example?

• Ans 1: The solubility is defined as the concentration of the solute in the solution when it is in equilibrium with the solid substance at a particular temperature. Solubility is expressed in terms of number of grams of solute in 100g of solvent. At a particular temperature, saturated solution of NaCl in water at O° C contains 37.5g NaCl in 100g of water.

Why is the vapour pressure of a solution less than pure solvent?

• Ans 1: In pure solvent all the surface of solvent is covered by solvent molecules.But when a solute is added to it from a solution.Some surface is occupied by solute particles. Hence escaping tendency of solvent is decreases and thus vapour pressure of solution also lowered.

One molal solution of urea in water is dilute as compared to one molar solution of urea but the number of practices of solute is same.Justify it?

• Ans 1: Both one molar and one molal urea solution contains equal number of molecules(6.022x10²³ ).Number of water molecules are different in both cases.One molal solution contains 1000g or 55.5 moles of water.One Molar solution has less number of water molecules than one molal.

Define consulate solution temperature with example (what is consulate temperature)?

• Ans 1: Consulate Temperature: The temperature at which two conjugate solutions merge into each other to form homogeneous mixture is called critical solution temperature or consulate temperature.e.g Water -Aniline has consulate temperature 167°C with 15% H₂O.

Define molal freezing point constant giving example.

• Ans 1: It is depression of freezing point, when one mole of non-volatile and non-electrolyte solute is dissolved in one kg of solvent.

Give the condition of colligative properties?

• Ans 1: There are following conditions for colligative properties:
  1. Solution must be dilute.
  2. Solute must be non-volatile.
  3. Solute must be non-electrolyte.

One molal solution of urea is more dilute as compared to its one molar solution.Why?

• Ans 1: One molal solution contains one mole of urea per kg of solvent, while one mole solution contains one mole of urea per one dm³ Of solution.In one molal solution amount of water is greater than one molar solution because amount of solution included in it.

Why the solubility of glucose increases on increasing temperature?

• Ans 1: When glucose is dissolve in water it show endothermic heat of solution.Solute molecules separate from each other to dissolve in solvent.This process required energy.So when temperature is increased solubility also increases.

The concentration in terms of molality is independent of temperature but molarity depends upon temperature .Why?

• Ans 1: In molality mass of solvent is taken.Mass us independent of temperature.In molarity volume of solution is take.Volume changes by change in temperature.