1here we consider ethanol to be the solvent.
vapour pressure of solution = vapour press. of pure solvent * its mole fraction in solution.
thus v.p. M = 40*0.9=36 mm Hg
11 Answers
11I had the same doubt. I suppose since ethanol is present in large amount as compared to water we consider it as the solvent. can someone clarify ?
262swaraj, i agree with you.
but in the fiitjee solns as well as jee official soln. Answer given is 36mm Hg
1Since ethanol molecules will be in such excess, water molecules exposed to the surface will be very less, hence its vapour pressure should be neglected.
262i dont think they can be neglected. it isnt too small to be neglected.
Any other reasons ??
71Aditya, the answer is 39.3 mm Hg. I had a recent visit to International Book fair here in Kolkata. I looked for solutions of this question in IIT past years available there from few publishers.
Indeed, the answer given in that book was 39.3 mm Hg. So, Don't worry.
262but i have checked the solutions provided in iit website and they have also given 36 as the correct answer.
http://www.iitkgp.ernet.in/jee/
check out the above link.