[ritwik08]

An empty flask open to air weighed 24.173 gram. The flask was filled with the vapour of an organic liquid and was sealed off at the barometric pressure and at 100 C. At the room tmperature the flask then weighed 25.002 gram. The flask was thn opened and filled with water at room temperature after which it weighed 176 gram. The barometric reading was 725 mm Hg. All weighings are done at the temperature of the room which is 25 C. What is the molar mass of the organic vapour? Allow for the byuoyancy of air in the weighing of the sealed off flask, using 1.18 g/L for the density of air at 25 C and 1 atm.

My attempt:
Case 1:
The first weighing gives the weight of the empty flask=24.173 gram
Byouyant force negligible.
Case 2:
Wt. of vapour+flask-byuoyant force= 25.002
Case 3:
Wt.of flask+ water--byuoyant force=176

I assumed the density of water = 1gm/ cc and then calculated the volume of the vessel=152 cc
I then calculated the molar mass of the organic vapour using PV=nRT but my answer doesnt match. Help me!!