Ideal & Non-ideal sols

Member Name

• Adnan Shaukat
• Talha Butt
• Burhan Nawaz
• Atiq ur Rehman
• Naseer ul Din
• Zubair khalid

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Non-ideal solution(Real solution):-

• Such mixture are real solution or non ideal solution that do not adhere Raoult’s law throughout the entire range pf composition

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• Many pair of liquid in which there is no uniformity of attraction force i-e the adhesive &cohesive force of attraction are not uniform between the two liquids , so that they show deviation from the Raoult’s law which is applied only to ideal solution

1-Negative deviation :-

• When adhesive force between molecules of A&B are greater than the cohesive force between A&A or B&B, then the vapor pressure of the solution is less than the expected vapor pressure from Raoult law. This is called negative deviation from Raoult’ law . These cohesive force are lessened not only by dilution but also attraction between two molecules through formation of hydrogen bonds . This will further reduce the tendency of A and B to escape
• For Example;

chloroform & acetone such as attraction by formation of an H-bond

2-Positive Deviation

• When the cohesive forces between like molecules are greater than the adhesive forces, the dissimilarities of polarity or internal pressure will lead both components to escape solution more easily. Therefore, the vapor pressure will greater than the expected from the Raoult law showing positive deviation. If the deviation is larger, then the vapor pressure curve will show a maximum at a particular composition
• For Example:-

Benzene &ethyl alcohol,

carbondisulphide ethanol etc…

Ideal Solution:-

• An ideal solution as one in which there is no change in the properties of components other than dilution when they are mixed to form the solution
• No heat evolved or absorbed during mixing process
• No change in the volume occur at final solution no shrinkage and no expansion
• The constitute properties

For example:

vapor pressure , refractive index , surface tension and viscosity of the solution are the weighted average of the properties of pure indiviual constitute

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Cont..

• ideal solution is formed by mixing substance with similar properties

For Example :

when 100 ml of methanol is mixed with 100 ml of ethanol the final volume of solution is 200 ml and no heat evolved or absorbed. The solution is nearly ideal

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Ideal solution and Raoult’law

• Raoult law recognized that in an ideal solution the partial pressure of each volatile constituent is equal to the vapor pressure of the pure constituent multiple by its mole fraction in solution
• For A&B
• pA=pAxA
• pB=pBxB�

Ideal solution and Raoult law

• pA and pB are the partial pressure of the constituent over the solution .when the mole fraction concentration is xA and xB the vapor pressure of pure components are pAa and PBb

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• For example :-
• if the vapor pressure of ethylene chloride in pure state is 236mmHg at 50oC then in a solution. Consisitingof a mole fraction of 0.4 ethylene chloride and 0.6 benzene . The partial pressure of CH2cl is 40% of 236mm or 94.4 . In ideal solution liquid A and B present in a final solution . This will diminish the escaping tendency of each constituent leading to reduce the rate of escape of the molecules of A and B from the surface