CBSE Class 12 Chemistry Revision Solutions. Learning the important concepts is very important for every student to get better marks in examinations. The concepts should be clear which will help in faster learning. The attached concepts will help the student to understand the chapter and score better marks in the examinations.
Solution is the homogeneous mixture of two or more substances in which the components are uniformly distributed into each other. The substances which make the solution are called components. Most of the solutions are binary i.e., consists of two components out of which one is solute and other is solvent. Ternary solution consists of three components
Solute - The component of solution which is present in smaller quantity.
Solvent – The component of solution present in larger quantity or whose physical state is same as the physical state of resulting solution.
Types of solutions: Based on physical state of components solutions can be divided into 9 types.
Solubility - The amount of solute which can be dissolved in 100grm of solvent at particular temp. to make saturated solution.
Solid solutions are of 2 types -
1. Substitutional solid solution e.g. Brass (Components have almost similar size)
2. Interstitial solid solution e.g. steel (smaller component occupies the interstitial voids)
Expression of concentration of solution
1. Mass percentage= amount of solute present in 100grm solution.
For liquid solutions percentage by volume is expressed as = volume of solute(VB) / volume of solution (VA+VB)*100
2. Mole fraction it is the ratio of no. of one component to the total no. of moles of all components. It is expressed as ‘x’. For two component system made of A and B ,XA= nA +nB , XB= nA+nB , Sum of all the components is 1 ; XA+XB =1
3. Molarity (M)= No.of moles solute/ volume of solution(L)
It decreases with increase in temperature as volume of solution increases with temperature.
4. Molality (m) = no of moles of solute/ mass of solution(in kg)
No effect of change of temperature on molality as it is mass to mass ratio.
5. Normality (N) = no.of gram equivalent of solute/ volume of solution(L)
It changes with changes temperature.
6. Parts per million (ppm) concentration of very dilute solution is expressed in ppm.
Vapor pressure – It is defined as the pressure exerted by the vapour of liquid over the liquid over the liquid in equilibrium with liquid at particular temperature vapour pressure of liquid depends upon nature of liquid and temperature.
Roult’s Law –
1. For the solution containing non-volatile solute the vapor pressure of the solution is directly proportional to the mole fraction of solvent at particular temperature
PA = P0A.XA
2. For the solution consisting of two miscible and volatile liquids the partial vapor pressure of each component is directly proportional to its own mole fraction in the solution at particular temperature.
PA=P0A. XA , PB=P0B .XB
And total vapor pressure is equal to sum of partial pressure. Ptotal = PA + PB
Ideal solution – The solution which obeys Roult’s law under all conditions of temperature and concentration and during the preparation of which there is no change in enthalpy and volume on mixing the component.
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