Medium MCQ +4 / -1 PYQ · JEE Mains 2020

At 35oC, the vapour pressure of CS2 is 512 mm. Hg and that of acetone is 344 mm Hg. A solution of CS2 in acetone has a total vapour pressure of 600 mm Hg. The false statement amongst the following is :

  1. A CS<sub>2</sub> and acetone are less attracted to each other than to themselves.
  2. B a mixture of 100 ml. CS<sub>2</sub> and 100 ml. acetone has a volume &lt; 200 ml. Correct answer
  3. C Heat must be absorved in order to produce the solution 35<sup>o</sup>C
  4. D Raoult's law is not obeyed by this system.

Solution

As the vapour pressure of mixture increases so the force of attraction of mixture is less than the individual component. <br><br>Since the vapour pressure of the solution is greater than individual vapour pressure of both pure components, the solution shows a positive deviation from Raoult’s law. <br><br>$\therefore$ $\Delta$<sub>Sol</sub>H $&gt;$ 0 <br><br>As $\Delta$<sub>Sol</sub>H $&gt;$ 0 then solution is endothermic. <br><br> and here $\Delta$<sub>Sol</sub> Volume $&gt;$ 0. As $\Delta$<sub>Sol</sub> Volume $&gt;$ 0 then a mixture of 100 ml. CS<sub>2</sub> and 100 ml. acetone has a volume more than 200 ml. It happens because the distance between molecules increases due to force of attraction of mixture decreases.

About this question

Subject: Chemistry · Chapter: States of Matter · Topic: Gas Laws

This question is part of PrepWiser's free JEE Main question bank. 142 more solved questions on States of Matter are available — start with the harder ones if your accuracy is >70%.

Drill 25 more like these. Every day. Free.

PrepWiser turns these solved questions into a daily practice loop. Chapter-wise drills, full mocks, AI doubt chat. No auto-renew.

Start free →