# Which is correct w.r.t non-ideal solution? Option 1) Solution obeys Raoult's Law over the entire range of concentration.  Option 2) The vapour pressure is always higher than that predicted by Raoult's Law Option 3) The cause for the deviations lie in the nature of interactions at the molecular level Option 4) All of these

Answers (1)
V Vakul

As learnt in

Condition for positive deviation -

When A - A interactions and B - B  interactions  are  stronger than A - B interactions.

e.g. Ethanol + water

- wherein

$\Delta H_{mix}> 0$

$\Delta V_{mix}> 0$

$(V_{f}>V_{A}+V_{B} )$

$\Delta H - Change\: in\: enthalpy$

$\Delta V - Change\: in\: volume$

Condition for negative deviation -

When A - A interactions and B - B  interactions  are  weaker than A - B interactions.

e.g. Acetone + Chloroform

- wherein

$\Delta H_{mix}< 0$

$\Delta V_{mix}< 0$

$(V_{f}< V_{A}+V_{B} )$

$\Delta H - Change\: in\: enthalpy$

$\Delta V - Change\: in\: volume$

Any solution that shows deviation from Raoult's law is called a non-ideal solution. Direction can be both positive and negative.
Positive deviation is observed when A-A interactions are stronger than A-B interactions.
Negative deviation is observed when A-A and B-B interactions are weaker than A-B interactions.

Option 1)

Solution obeys Raoult's Law over the entire range of concentration.

This solution is incorrect

Option 2)

The vapour pressure is always higher than that predicted by Raoult's Law

This solution is incorrect

Option 3)

The cause for the deviations lie in the nature of interactions at the molecular level

This solution is correct

Option 4)

All of these

This solution is incorrect

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