Question

30 grams of unknown solute are dissolved in 156grams of benzene the vapour pressure of pure benzene is 200 mmHg and that of the solution is 150 mmHg .find the molecular mass of solute​

Answer 1

Answer:

Answer :

65.25 g mol−1

Solution :

P∘A=640 mm Hg, PS=600 mm Hg, WB=2.175h,WA=39.0g.

MA(C6H6)=78 g mol−1

According to Raoult's Law (solution is ideal or dilute),

P∘A−PSPS=nBnA=WBMB×MAWA

(640−600)mm600mm=(2.175g)(MB)×(78 g mol−1)(39.0g)

MB=(2.175g)×(78 g mol−1)(39.0g)×(78 g mol−1)(40mm)=65.25 g mol−1.