Which one of the following is incorrect for a solution having negative deviation?
I)ΔHmix< 0
II)ΔSmix< 0
III)ΔGmix< 0
IV)ΔVmix< 0

Dear Student

i) For negative deviation from Raoults law, solute-solvent interaction is stronger than solute-solute and solvent-solvent interactions. So when a solution shows negative deviation the energy released in forming solute-solvent interaction will be greater than that of energy required to break solute-solute and solvent-solvent interactions. Hence ΔHmix< 0

ii) When two solutions are mixed, either of ideal/non ideal (showing negative or positive deviation any), ΔSmix>0 always, because when two solutions are mixed the molecules get a greater volume to move and hence their randomness will always increase.

iii) As the dissolution is occuring without any external factor given, the reaction is spontaneous and hence ΔGmix< 0

iv) Now when two solutions are mixed which shows negative deviation as we said,  solute-solvent interaction is stronger than solute-solute and solvent-solvent interactions, the stronger solute-solvent interaction will somehow decrease the volume of mixing just a bit. So ΔVmix< 0

Hence option ii is correct for question asked.

Regards
 

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