Question

A solution prepared by dissolving 26.0 mmol naphthalene (nonvolatile) in 92.0 mmol benzene will have a vapor pressure of ________mm Hg. The vapor pressure of pure benzene at 25 °C is 95.1 mm Hg.
      
Answer not listed
       
146
       
26.9
       
21.0
       
41.9
       
62.8
       
74.1

Answer 1

Milli-moles of Napthalene = 26 m-mol

Milli-moles of Benzene = 92 m-mol

Mole Fraction of Benzene = (92 m-mol)/(26 m-mol + 92 m-mol), xbenzene = 0.780

Vapor Pressure of Pure Benzene, P0benzene = 95.1 mm Hg

According to Raoult's Law,

Vapor Pressure of the Solution, Psolution = (xbenzene)(P0benzene ) = (0.780)(95.1 mm Hg) = 74.1 mm Hg

Therefore, the vapor pressure of the given solution is 74.1 mm Hg. Correct Answer is Option (7).