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.

Define percentage weight/weight.Give an example?

• Ans 1:

In summer the antifreeze solutions protect the radiations from boiling over.How?

• Ans 1: The boiling point of liquid is increased by the addition of solute such as ethylene glycol in water.Therefore in summer the antifreeze liquids protect the water in car radiators from over boiling. Similarly the addition of a solute in water depress its freezing point. During winter it protect a car by preventing the liquid from freezing in radiators.

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.

Beckmann's thermometer is used to note the depression in freezing point.Explain with reason?

• Ans 1: There is a very small difference between freezing point of pure solvent and its dilute solution.Ordinary thermometer can read up to 0.5K.Hence theses cannot differentiate between freezing point of pure solvent and solution.
  Beckmann' sthermometer can read up to 0.01K.Hence it cn exactly measure the freezing point of pure solvent and solution.

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.

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.

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
  

Define Colligative properties.Name important colligative properties?

• Ans 1: Colligative Properties: The properties of a solution which is based upon the number of solute particles and independent of the nature of solute is called colligative properties.Name of some colligative properties are:
  1. Lowering of vapour pressure
  2. Depression in freezing point
  3. Elevation in boiling point
  4. Osmotic pressure

Define azeotropic mixture.Give two examples?

• Ans 1: Azeotropic Mixtures: The liquid mixtures which boil at constant temperature and distil over without changes in composition like a pure compound at any temperature is called azeotropic mixtures.e.g.HCI azeotropic mixture with water.

The total volume of the solution by mixing 100 cm³ Of water 100 cm³ Of alcohol may not be equal to 200 cm³ Justify it?

• Ans 1: Alcohol and water are mix in all proportions.However, the properties of such solutions are not strictly additive.Generally, the volume decreases ,mixing but in some cases it increases.Heat may be evolved or absorbed during the formation of such solutions.

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 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.

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.

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.

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.

Differentiate between ideals and non-ideal solutions?

• Ans 1: Ideal Solution:
  1. The solutions which obey Raoult's law are called ideal solution
  2. In these solution, enthalpy change is zero.

  
  
• Ans 2: Non-Ideal Solution:
  1. The solutions which do not obey Raoult's law are called non-ideal solution
  2. In theses solutions, enthalpy change is not zero.

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 some properties are called colligative properties?

• Ans 1: Colligative properties are called so because these depend upon the number of solute particle in definite amount of solvent and independent on the nature of solute.For example lowering of vapour pressure of water, caused by the addition of 6g of urea, 18 g of glucose and 34.2 g of sucrose is same although the solute particles are of different nature but their numbers are same.

Calculate percentage by weight of NaCI when 2g of NaCI is dissolved in 20g of water?

• Ans 1: Mass of NaCl =2g
  Mass of water =20g
  Mass of solution= 20+2=22g
  %by weight of NaCl=2/22x100=9.09%

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 .

In summer the antifreeze solutions protect the radiations from boiling over.How?

• Ans 1: The boiling point of liquid is increased by the addition of solute such as ethylene glycol in water.Therefore in summer the antifreeze liquids protect the water in car radiators from over boiling. Similarly the addition of a solute in water depress its freezing point. During winter it protect a car by preventing the liquid from freezing in radiators.

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.

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.

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.

Differentiate between ideals and non-ideal solutions?

• Ans 1: Ideal Solution:
  1. The solutions which obey Raoult's law are called ideal solution
  2. In these solution, enthalpy change is zero.

  
  
• Ans 2: Non-Ideal Solution:
  1. The solutions which do not obey Raoult's law are called non-ideal solution
  2. In theses solutions, enthalpy change is not zero.

Can sugar cannot be dissolved in benzene.Give reason?

• Ans 1: Can-sugar is apolar covalent substance and it is soluble in polar solvent like water. Sugar dissolve in water due to the formation of H-bonding between solute-solvent,but not in benzene.As we simply say that solubility based upon principle"Like dissolves like".

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.

Define Colligative properties.Name important colligative properties?

• Ans 1: Colligative Properties: The properties of a solution which is based upon the number of solute particles and independent of the nature of solute is called colligative properties.Name of some colligative properties are:
  1. Lowering of vapour pressure
  2. Depression in freezing point
  3. Elevation in boiling point
  4. Osmotic pressure

The total volume of the solution by mixing 100 cm³ Of water 100 cm³ Of alcohol may not be equal to 200 cm³ Justify it?

• Ans 1: Alcohol and water are mix in all proportions.However, the properties of such solutions are not strictly additive.Generally, the volume decreases ,mixing but in some cases it increases.Heat may be evolved or absorbed during the formation of such solutions.

The total volume of the solution by mixing 100 cm³ Of water 100 cm³ Of alcohol may not be equal to 200 cm³ Justify it?

• Ans 1: Alcohol and water are mix in all proportions.However, the properties of such solutions are not strictly additive.Generally, the volume decreases ,mixing but in some cases it increases.Heat may be evolved or absorbed during the formation of such solutions.

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.

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.

Describe that NaCI and KNO₃ Are used to lower the melting point of ice?

• Ans 1: NaCI and KNO₃are used as antifreeze.They depress the freezing point of ice and it melts. This method is used to melt the ice from the roads in winter.

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.

Give two examples of liquid solution?

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

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.

• Ans 1:

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 azeotropic mixture.Give two examples?

• Ans 1: Azeotropic Mixtures: The liquid mixtures which boil at constant temperature and distil over without changes in composition like a pure compound at any temperature is called azeotropic mixtures.e.g.HCI azeotropic mixture with water.