⭐ Revision in shorts 🔻Raoult’s Law: “The partial vapour pressure of any component in the solution is directly proportional to its mole fraction”. For a binary solution of two components A and B, PA = XA PB = XB Where P0A = vapour pressure of component A in pure state. PA = vapour pressure of component A in the solution. P0B = vapour pressure of component B in pure state. PB = vapour pressure of component B in the solution 🔻Limitations of Raoult’s Law:-) Raoult’s law is applicable only to very dilute solutions. 🔻It is applicable to solutions containing non-volatile solute only. 🔻It is not applicable to solutes which dissociate or associate in a particular solution 🔻Raoult’s Law in Combination with Dalton’s Law of Partial Pressure: PT = XA P0A + XB P0B = P0B + (P0A -P0B) XA Where PT = Total Vapour Pressure of the Solution. Ideal and Non-Ideal Solutions: 🔻Ideal Solution: These solutions obey Raoult’s law at all compositions of solute in solvent at all temperature Two liquids A and B form and ideal solution when A –A and B–B molecular attractions will be same and hence A–B molecular attraction will be almost same as A–A and B–B molecular attraction. 🔻For Ideal Solution: 1. dHmixing = 0, i.e. no heat should be absorbed or evolved during mixing 2. dVmixing = 0, i.e. no expansion or contraction on mixing Examples , Ethyl chloride and ethyl bromide, n–hexane and n–heptane , CCl4 and SiCl4 🔻Non-Ideal Solution: These solutions deviate from ideal behaviour and do not obey Raoult’s law over entire range of composition. For non ideal solutions, 1. dHmixing ≠ 0 2. dHmixing ≠ 0 Here we may have two cases A) Positive Deviation: 1. PA > XA & PB > XB 2. dHmix > 0 3. dVmix > 0 Example: Cyclohexane and Ethanol B) Negative Deviation: 1. PA > XA & PB > XB 2. dHmix < 0 3. dVmix < 0