How would your results be affected if you didn\'t remove the rubber band before

Question

How would your results be affected if you didn't remove the rubber band before weighing the flask and the condensed liquid vapor? If you wished to determine the molar mass of a liquid with a boiling point of 140degree C, what modifications would have to be make to this experiment? 4,500 mL of an unknown organic liquid (Specific Gravity = 0.785) was placed in a flask and vaporized as in this experiment. Data obtained follows: weight of vapor: 0.629 g temperature of vapor: 100degree C volume of vapor: 147 mL pressure of vapor: 760.2 torr Using the above data, calculate experiment molar mass. Calculate mL of the liquid that condensed.

Explanation / Answer

Molecular weight of a volatile liquid

3) To measure the molecular weight of a boiling liquid at 140 oC, we must accurately weigh the vapor collected/formed. The system should be perfectly closed such that any vapor formed does not leave the system.

4) For the unknown vapor molar mass

(a) experimental molar mass = gRT/PV

with,

g = 0.629 g

R = gas constant

T = 100 + 273 = 373 K

P = 760.2 torr = 1 atm

V = 147ml = 0.147 L

we get,

molar mass = 0.629 x 0.08205 x 373/1 x 0.147 = 130.95 g/mol

(b) Volume of liquid condensed = 0.629 g/0.785 = 0.801 ml

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