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

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
  

The freezing points are depressed due to the presence of solutes.Five reason?

• Ans 1: Freezing point of a substance also related to its vapour pressure.it is a temperature at which there is equilibrium between a solid and a liquid. At freezing point, vapour pressure of liquid and solid phase is same.When some solute is added to solvent, its vapour pressure decreases and freezing point also decreases.

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.

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.

What is upper consulate temperature and give one example?

• Ans 1: The temperature of 65.9°C at which two conjugate solutions merge into one another is called critical solution temperature or upper consulate temperature .For Example 34% phenol and 66% water solution.

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.

Give two examples of liquid solution?

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

Give conjugate solution with one example.

• Ans 1: Each liquide layer of solution of two liquids which are not miscible with each other is a saturated solution of the other liquid.Such solutions are called conjugated solutions.On shaking equal volumes of water and ether, two layers are formed which is example of conjugated solution.

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 percentage weight/weight.Give an example?

• Ans 1:

Why ethylene glycol is added in radiator of Automobile?

• Ans 1: The most important application of this phenomenon is the use of antifreeze in the radiator of an automobile.The solute is ethylene glycol, which is not only completely miscible with water but has a very low vapour pressure and non-volatile in character. When mixed with water it lowers the freezing point a swell as raised the boiling point.

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.

Polar solids are not dissolved in on-non-polar solvent,give reason?

• Ans 1: There is a general principal that "like dissolve like".That;s why polar compounds are not dissolve in non-polar solvent because their nature matches with each other.

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.

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.

Give conjugate solution with one example.

• Ans 1: Each liquide layer of solution of two liquids which are not miscible with each other is a saturated solution of the other liquid.Such solutions are called conjugated solutions.On shaking equal volumes of water and ether, two layers are formed which is example of conjugated solution.

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.

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 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.

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.

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 "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 .

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 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.

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 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.

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.

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.

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.

• Ans 1:

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.

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.

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.

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.

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%

Why ethylene glycol is added in radiator of Automobile?

• Ans 1: The most important application of this phenomenon is the use of antifreeze in the radiator of an automobile.The solute is ethylene glycol, which is not only completely miscible with water but has a very low vapour pressure and non-volatile in character. When mixed with water it lowers the freezing point a swell as raised the boiling point.

The freezing points are depressed due to the presence of solutes.Five reason?

• Ans 1: Freezing point of a substance also related to its vapour pressure.it is a temperature at which there is equilibrium between a solid and a liquid. At freezing point, vapour pressure of liquid and solid phase is same.When some solute is added to solvent, its vapour pressure decreases and freezing point also decreases.

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.

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.