NCERT CLASS 12 COMPLETE NOTES CHEMISTRY CHAPTER 1 SOLUTIONS

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SOLUTIONS

This chapter will deal mostly with liquid solutions and their formation. So, let’s get started.

 WHAT ARE SOLUTIONS?

Solutions are homogeneous mixture of two or more than two component. On the basis of components, SOLUTIONS are divided into following types:-

• BINARY-having two components
• TERNARY- having three components
• QUARTERNARY- having four components

In this class we will limit our discussion to two component solutions i.e. BINARY solutions. So, a binary solution has two parts namely SOLUTE and SOLVENT. i.e.
solute+solvent=solution

SOLVENT is that part of solution which is present in largest quantity and determines the physical state of solution.

EXPRESSING  CONCENTRATIONS  OF  SOLUTIONS:-

A famous quote says that, a thing which gets measured gets improved. So, it’s important to use some measurement techniques that will give quantitative description of CONCENTRATION of solution.

Reiterating some basic expressions read in class 11^th:-

MASS PERCENTAGE (w/w):- 

Mass % of a component=mass of the component in the solutiontotal mass of the solution ×100

VOLUME PERCENTAGE (V/V):-

Volume  % of a component=volume of the component in the solutiontotal volume of the solution ×100

MASS BY VOLUME PERCENTAGE (m/V):- It is the mass of solute dissolved in 100ml of the solution. 

E.g. – Amount of dissolved oxygen is water, amount of chlorine in supply drinking water, amount of  SO2 in air

PARTS PER MILLION (ppm) when the solute is present is trace quantities, the concentration is expressed in ppm

MOLE FRACTION- It is defined as

 Mole fraction of a component=
No.of moles of a component/Total no.of moles of all components

If A and B are two components, then
xA=nAnA+nB

Also, Solution containing i number of components:-

x1 +x2+x3+…+xi=1

MOLARITY (M):- It is defined as the no. Of moles dissolved in 1L solution.

MOLALITY (m):– It is defined as the number of moles of solute present in 1kg solvent.

Molality (m)=Moles of solute/mass of solvent in  kg

SOLUBILITY

Solubility of a substance is defined as the maximum amount that can be dissolved in a specified amount of solvent at a specified temperature.

1. SOLUBILITY OF SOLID IN A LIQUID

In general, a solute dissolves in a solvent if the intermolecular interactions are similar in the two or we may say

 Like dissolves like.

When a solid solute is added to the solvent, then two processes take place–

1. DISSOLUTION:-When a solid solute is added to the solvent, some solute dissolves and its concentration increases in solution. This process is known as Dissolution.

2. CRYSTALLISATION:–  Some solute particles in solution collide with the solid solute particles and get separated out of solution. This process is known as crystallization.

A stage is reached when the two processes occur at the same rate. Under such conditions, number of solute particles going into solution will be equal to the solute particles separating out and a state of dynamic equilibrium is reached.

Solute + Solvent = Solution

SATURATED SOLUTION: – The concentration of solution in which no more solute can be dissolved  at the same temperature and pressure, is called a SATURATED  SOLUTION.

For detailed notes, please download the NCERT Complete notes of solutions PDF given above.