Dumas Experiment filled, it has a volume of 268 temperature 11. Reexpress the te

Question

Dumas Experiment filled, it has a volume of 268 temperature 11. Reexpress the temperature of the water bath in units of Kelvin. the Dumas experiment, a pinholed flask apparatus has an empty mass of 216.422 g. When it's completely mpletely evaporate when immersed in a boiling water bath at 100.9°C. Upo 5 mL.. It's filled with a few milliliters of a volatile solvent which is the flask mass has increased to 217.504 g. The atmospheric pressure is on removal and cooling to roo 29.97 inches of Hg. 12. Reexpress the atmospheric pressure in units of atmospheres. (1.000 atm 29.92 inches of Hg) 13. Reexpress the volume of the apparatus in units of liters. 14. Calculate the moles of gas contained within the flask at the water bath temperature. 15. Use the above information to calculate the molar mass of the gas. 16. Suppose that only half of the height of the flask is immersed in boiling water. No solvent condenses at the top. In which direction will this throw off the final result for the molar mass? Explain why.

Explanation / Answer

Dumas experiment

11. Temperature (T) = 100.9 oC + 273 = 373.9 K

12. Pressure (P) = 29.97 inch Hg/29.92 inch Hg = 1.002 atm

13. Volume (V) = 268.5 ml/1000 = 0.2685 L

14. moles of gas (n) = PV/RT

with, R = gas constant

So,

moles of gas (n) = 1.002 x 0.2685/0.0821 x 373.9 = 0.0088 mol

15. mass of gas = 217.504 - 216.422 = 1.082 g

molar mass of gas = grams/moles = 1.082/0.0088 = 122.954 g/mol

16. If only half of the flask is immersed in boiling water, not all the liquid has evaporated. The final mass of gas in the flask would be lower. Therefore, the molar mass calculated would be also lower than actual value. molar mass is directly related to mass of gas in the flask.

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