Question

Two cases arise:(i) a > 0 (ii) a < 0

Answer 1

Answer:

Positive deviation from Raoult's law occurs when the total vapour pressure of the solution is more than corresponding vapour pressure in case of ideal solution.

P=P A +P B>P Ao X A +P BoX B

Negative deviation from Raoult's law occurs when the total vapour pressure of the solution is less than corresponding vapour pressure in case of the ideal solution.

P=P A +P B<P A o X A+P Bo X B

For positive deviation from Raoult's law, Δ

mmi H has a positive sign.

For negative deviation from Raoult's law, Δ

mix H has a negative sign.