An empty 149 mL flask weighs 68.322 g before a sample of volatile liquid is added. The flask is then placed in a hot (95.0°C) water bath; the barometric pressure is 740 torr. The liquid vaporizes and the gas fills the flask. After cooling, flask and condensed liquid together weigh 68.697 g. What is the molar mass of the liquid?

MW liquid = 77.811 g/mol

In general, the gas equation can be written  

PV=nRT  

where  

P = pressure, atm , N/m²  

V = volume, liter  

n = number of moles  

R = gas constant = 0.082 l.atm / mol K (P= atm, v= liter),or 8,314 J/mol K (P=Pa or N/m², v= m³)  

T = temperature, Kelvin  

P = 740 torr = 0.973684 atm

V = 149 ml = 0.149 L

T = 95 °c = 95+273 = 368 K

input in formula :

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