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Questions
Distinguish between ideal and non-ideal solutions.
Using the Raoult’s law, how would you distinguish between ideal and non-ideal solutions?
Mention the main points of difference between ideal and non ideal solutions.
Mention the main points of difference between ideal and non ideal (both showing positive as well as negative deviations) solutions. Give at least two examples of each type.
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Solution 1
| Ideal solutions | Non-ideal solutions | |
| 1. | Ideal solutions obey Raoult’s law over the entire range of concentrations. | Nonideal solutions do not obey Raoult’s law over the entire range of concentrations. |
| 2. | The vapour pressure of an ideal solution always lies between the vapour pressures of pure components. | The vapour pressures of these solutions can be higher or lower than those of pure components. |
| 3. | Solvent-solute, solute-solute and solvent-solvent molecular interactions are comparable. | Solute-solvent intermolecular attractions may be weaker or stronger than those between solute-solute molecules and solvent-solvent molecules. |
| 4. | e.g. Benzene + toluene, n-Hexane + n-Heptane | e.g. Ethanol + acetone Carbon disulphide + acetone Phenol + aniline Chloroform + acetone, Acetone + ethanol (CH3COCH3 + C2H5OH) |
Solution 2
| Sr. No. | Ideal solution | Non-ideal solutions | |
| Solutions showing positive deviation | Solutions showing negative deviations | ||
| 1. | A-B molecular interaction forces are similar to A-A or B-B molecular interaction forces. | A-B molecular interaction forces are weaker than A-A or B-B molecular interaction forces. | A-B molecular interaction forces are stronger than A-A or B-B molecular interaction forces. |
| 2. | pA = pA° χA; pB = pB° χB |
pA > pA° χA; pB > pB° χB |
pA < pA° χA; pB < pB° χB |
| 3. | No heat is evolved or absorbed during dissolution. | Dissolution is endothermic. | Dissolution is exothermic. |
| 4. | `Delta H_"mixing" = 0` | `Delta H_"mixing" > 0` | `Delta H_"mixing" < 0` |
| 5. | `Delta V_"mixing" = 0` | `Delta V_"mixing" > 0` | `Delta V_"mixing" < 0` |
| 6. | Do not form azeotropic mixtures. | Form minimum boiling azeotropic mixtures. | Form maximum boiling azeotropic mixtures. |
Notes
Students should refer to the answer according to their questions.
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