Question

For a non-ideal solution exhibiting positive deviation from Raoult's law, ${\Delta }_{mix}H$ has a ............... (nonzero)

• A. positive
• B. negative
• C. zero
• D. none

Answer 1

The correct option is A positive

Positive deviation from Rault's law: This deviation is shown when the forces of attraction between $A-B$ molecules are less than forces of attraction between $A-A$ and $B-B$ molecules in the two liquids forming the solution.
The total vapour pressure of the solution will be greater than the corresponding vapour pressure expected in case of the ideal, an ideal solution of the same composition. i.e.
${\Delta }_{mix}H>0$
${\Delta }_{mix}V>0$