Question

Octane and nonane forms nearly ideal binary
solution. When 1.0 mL of octane is added to
100 mL of nonane, the boiling point of solution
falls. Which of the following is true about octane
and nonane at same temperature?
(1) Pure octane has lower vapour pressure than
pure nonane.
(2) Pure nonane has lower vapour pressure than
pure octane.
(3) The solution formed above has lower vapour
pressure than both pure octane and pure
nonane.
(4) The solution formed above has greater vapour
pressure than both pure octane and pure
nonane.​

Answer 1

Answer:

(3) The solution formed above has lower vapour

pressure than both pure octane and pure

nonane.

Explanation:



Mixture of Hydrocarbons follow Roults law and the given mixture is an Ideal Soultion

According to Henrys Law

Total pressure = PoA Xa + PoB Xb

Where PoA and PoB are the pressure of the Hydrocarbon at

Pure state.

And value of Xa and Xb will be less than one representing Mole fraction

Thus we conclude the value for solution will be less