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Keith puts 6.0 mL of a volatile liquid into a 2s4.3 mL flask. The Keith then put

ID: 523099 • Letter: K

Question

Keith puts 6.0 mL of a volatile liquid into a 2s4.3 mL flask. The Keith then puts the flask into a water bath at 96.3 degree C and heated until all of the liquid has turned to vapor. When the vapor is condensed, 0.355 g of the liquid is present. The external pressure is 772.8 torr. Calculate the molar mass of the volatile liquid (g/mol). Why can't this measurement be performed on a liquid with a boiling point of 117 degree C? How was the EXACT volume of the flask determined (be sure to include experimental details)?

Explanation / Answer

3. a. molar mass of volatile liquid

molar mass = grams x gas constant x temperature/pressure x volume

                    = (0.355)(0.08205)(273 + 96.3)/(772.8/760)(0.2543)

                    = 41.60 g/mol

b. If the boiling point of the liquid If is 117 oC, the water bath temperature is not sufficient to boil off this high boiling liquid and hence the experiment could not be performed.

c. The exact volume of the flask can be determined by pouring water into the flask in which the experiment was carried out and then measuring the volume of water using measuring cyllinder.