Type Here to Get Search Results !

Solutions for Class 12 Chemistry CBSE


Solution

A solution is a homogeneous mixture of two or more components and the particle size is smaller than 1 nm.

Example:

👉Sugar in water solution

👉Salt in water solutions

👉Soda water

A Solution has two components, one is solvent and the other is solute.

The component that dissolves the other component is called the solvent.Its quantity is more.

The component(s) that is/are dissolved in the solvent is/are called solute(s).Its quantity is less.

The solvent and solute can be in any state of matter i.e. solid, liquid or gas.

Properies of solution :

Properties of solutions are as follows:

👉Solution is a homogeneous mixture and stable

👉Its particles size are too tiny and have a diameter of less than 1 nm.

👉The particles of solution are not visible to naked eyes.

👉Particles don’t scatter a beam of light passing through it so the path of the light is not visible.

👉Solutes are inseparable from the mixture and do not sediment.

👉The components of a mixture cannot be separated by means filtration.

Question : Which of below statement is false about Solution?





Types of solution

Expressing Concentration of Solutions

Solubility

Solubility is the amount of solute that dissolves in a secified quantity of solvent at normal temperature.

Normal temperature means at 25°C (room temperature), but the solubility of a substance can change with different temperatures and pressure. For example, the solubility of most solids increases with temperature, while the solubility of gases generally decreases with increasing temperature.

👉Saturated solution: A solution that contains the maximum amount of solute that can be dissolved in it at a given temperature.

👉Unsaturated solution: A solution that contains less solute than the saturation level.

The concept 'like dissolves like' states that , non-polar organic compounds dissolve in non-polar organic solvent while polar inorganic compounds (salts) dissolve in polar solvent (water).

Vapour Pressure of Liquid Solutions

Pressure of vapour formed by the liquid (or solid) over the surface of the liquid at equlibrium (rate of evaporation is equal to rate of condensation) on a fixed temperature is called vapour pressure.

Vapour pressure increases with the temperature therefore It is defined at a given temperature . Vapour pressure depend on the nature of the liquid.

The boiling point of the liquid is the temperture when the pressure exerted by surrounding equals to the pressure exerted by vapor.

Characteristics of Vapour Pressure :

👉 A Pure liquid have greater of vapour pressure as as compared with liquid’s solution.

👉 Vapour pressure is inversely proportional to the forces of attraction existing between the molecules of a liquid.

👉 Vapour pressure increases with a rise in the temperature because the molecules gain kinetic energy and vapourise briskly.

Raoult's law

A French Chemist, Francois Marte Raoult had proposed a relationship between partial pressure and mole fraction of volatile liquids. According to the law, ‘the mole fraction of the solute component is directly proportional to its partial pressure’.

Let two volatile liquid components A (solvent ) and B (solute) of a solution has mole fractions XA and XB respectively.

In other way, Raoult's law states that at any temperature, partial vapour pressure of a volatile component of a solution is equal to multiplecation of the vapour pressure of that component and its mole fraction in solutions.

Ideal and Non-ideal Solutions

Ideal Solutions

Solution which obey Raoult’s Law at every range of concentration and at all temperatures are called Ideal solutions.It is formed by mixing two ideal components that are, solute and a solvent having similar molecular size and structure.

Let us consider two liquids A and B are mixed to make a solution. The resulting solution will experience several intermolecular forces of attractions inside it, They will be:

A – A intermolecular forces of attraction

B – B intermolecular forces of attraction

A – B intermolecular forces of attraction

If all three intermolecular forces of attactions ie forces of attraction between A – A, B – B and A – B are nearly equal. Then the solution will be ideal solotion.

An ideal solution is a solution meets the following conditions:

👉Obeys Raoult's law at all temperatures and concentrations.

👉Zero enthalpy of mixing.

👉Zero volume of mixing.

👉Similar intermolecular interactions.

👉Identical molecular size, structure, and intermolecular forces solute, solvent and solution.

Non-ideal Solutions

A solution, which does not obey Raoult's law for all the concentration and temperature ranges, it is known as a non-ideal solution.

A non-ideal solution meets the following conditions:

👉Donot obeys Raoult's law at any temperatures and concentrations.

👉Enthalpy of mixing is not zero.

👉Volume of mixing is not equal to zero.

👉Disimilar intermolecular interactions.

Positive deviation

The vapor pressure of the solution is higher than expected. This happens when the cohesion between like molecules is stronger than the adhesion between unlike molecules.

👉 Intermolecular forces of attraction for A – A,B – B is greater than A – B intermolecular forces of attraction

👉Enthalpy of mixing is positive.

👉Volume of mixing is positive.

The vapor pressure of the solution is lower than expected. This happens when the force between particles in the solution is weeker stronger than the force between particles in pure liquids.

Negative deviation

👉 Intermolecular forces of attraction for A – A,B – B is less than A – B intermolecular forces of attraction

👉Enthalpy of mixing is negative.

👉Volume of mixing is negative .

The vapor pressure of the solution is lower than expected. This happens when the force between particles in the solution is stronger than the force between particles in pure liquids.

Colligative Properties and Determination of Molar Mass

Abnormal Molar Masses

Azeotropic Mixture

Elevation in Boiling Point

Osmotic Pressure

Reverse Osmosis

Isotonic, Hypertonic, Hypotonic Solutions

Van’t Hoff Factor and Abnormal Molar Mass

Solubility and Henry’s Law

Numiricals

Q 1: Calculate the relative lowering of vapour pressure when 12g urea is dissolved in 90g of water?(Mol weight of urea :60 g/mol)





Q 2: 30 g of urea is dissolved in 846 g of water. Calculate the vapour pressure of water for this solution if vapour pressure of pure water at 298 K is 23.8 mm Hg.(Mol weight of urea :60 g/mol)





Q 3: What is the vapour pressure at 298K of a 20% solution of KNO3 by mass. Vapour pressure of water at 298K is 3.52kPa.(Molar mass of KNO₃ = 101 g/mol)




Click here for Explanation

cccccccccccccccccccccc


Q 4: If ethanol and chloroform are present in a molar ratio of 2:3 then what is the vapor pressure at 20° C if vapor pressures of pure liquids are 5.95 kPa and 21.17 kPa, respectively.




Click here for Explanation

Concept used Dalton's laws of totatl pressure


Show more