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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.
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 11th:-
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
Also, Solution containing i number of components:-
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 of a substance is defined as the maximum amount that can be dissolved in a specified amount of solvent at a specified temperature.
- 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–
- 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.
- 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.