CGPET 2021 Solved Paper

The solution prepared by mixing n-heptane and ethanol are non-ideal as n-heptane is non-polar and ethanol is polar. The stronger force of attraction between n-heptane- n-heptane and ethanol-ethanol are replaced by weaker force of attraction between n-heptane-ethanol in solution. Therefore, there will be increase in escaping tendencies of liquid molecules into vapour-phase which will increase vapour pressure more than expected value from Raoult's law. So, a positive deviation is observed.