MolSynapsequestion bank
MolSynapse / Question bank / Solutions and Colligative Properties / Relative lowering of vapour pressure
JEE Advanced levelOne or more correct optionsDifficulty 3 of 3so156

Four aqueous solutions are each made with kg of water at the same temperature (assume complete dissociation for electrolytes): S1 has mol glucose, S2 has mol , S3 has mol , S4 has mol urea. Which statements are correct?

  1. AS1 and S2 have the same vapour pressure.
  2. BS4 has the highest vapour pressure of the four.
  3. CS3 has the lowest vapour pressure of the four.
  4. DS4 has a lower vapour pressure than S2.

Answer: A, B, C

Count particles per kg of water: S1 0.20, S2 , S3 , S4 0.12 mol. Equal particle counts in equal water give equal vapour pressure, so S1 equals S2. S3 has the most particles and hence the lowest vapour pressure, and S4 has the fewest and hence the highest. S4 therefore has a higher, not lower, vapour pressure than S2.
Practice Solutions and Colligative Properties More on Relative lowering of vapour pressure
Previous questionNext question

More questions on Relative lowering of vapour pressure