Chemistry
posted by Shannon on .
An empty flask weighs 128.632g. After vaporization of a sample of volatile liquid, at a measured temperature of 99.8 C. The flask is sealed, cooled to room temperature, and weighed. The mass is now 129.225g. The measured P atm is 757.7 torr. The flask is rinsed and filled completely with water at 21.8 C. The mass of the flask is now 381.676g.
1. Calculate the volume of the flask from the mass of the water contained in the flask and the density.
2. Calculate the molar mass of the volatile liquid.

Can you do #1? volume = mass/density
#2. Use PV = nRT and solve for n = number of mols.
Substitute into moles = grams/molar mass. You have grams (from the mass flask + vapor  mass empty flask) and moles. Solve for molar mass. 
for #1, we have to find the density first right? so density is mass/volume, so from there you take 381.676 and divide that by..
and that's where im lost :( 
Close but no cigar.
381.676 = mass flask + water
128.632 = mass empty flask

difference = mass water
volume of flask = mass water/density water = ?? 
sorry to be asking too much but how do we get the density of water?