A binary liquid solution is prepared by mixing -heptane and ethanol. Which one of the following statements is correct regarding the behaviour of the solution ?
- (A)The solution formed is an ideal solution
- (B)The solution is non-ideal, showing + ve deviation from Raoult's law.✓ Correct
- (C)The solution is non-ideal, showing -ve deviation from Raoult's law.
- (D)n-heptane shows + ve deviation while ethanol shows -ve deviation from Raoult's law.
Answer: (B)
Solution
Pure ethanol is held together by hydrogen bonding, while -heptane is a non-polar hydrocarbon, and when the two are mixed the heptane molecules get between the ethanol molecules and weaken that hydrogen bonding. The new heptane–ethanol interactions are weaker than the average of the interactions in the pure liquids, so molecules escape more easily and the vapour pressure runs higher than Raoult's law predicts, a positive deviation.
JEE Main · 2009 · 12 Apr 2009 · Offline · Single correct option