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

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

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.

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 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.

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%

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.

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 .

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.

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 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.

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.

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 percentage weight/weight.Give an example?

• 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.

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.

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.

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.

NaCl and KNO₃ Lowers the melting point of ice.Give reason?

• Ans 1: When NaCl andKNO₃ Is added to H₂O , is vapour pressure is lowered. Due to lowering of vapour pressure, solution freezes below than the freezing point of water.Hence NaCl and KNO₃ Is used to lower the melting point of ice.

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.

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 solubility curve.Name its two types?

• Ans 1: Solubility Curve: A graphical representation between temperature and solubility of a substance is called solubility curve.These are of two types:
  1. Continuous solubility curve
  2. Discontinuous solubility cure

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.

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.

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.

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 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.

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 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.

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.

• Ans 1:

Define solubility curve.Name its two types?

• Ans 1: Solubility Curve: A graphical representation between temperature and solubility of a substance is called solubility curve.These are of two types:
  1. Continuous solubility curve
  2. Discontinuous solubility cure

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.

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 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

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.

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.

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 percentage weight/weight.Give an example?

• Ans 1:

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.