6. In the molecular weight determination by the Dumas method, as illustrated below,several grams of an organic liquid were drawn into the bulb. The bulb was then immersed ina water bath at 87 C and kept there until all the liquid was vaporized and the air in the bulbwas replaced by the vapor. The tip was then sealed shut and the bulb removed from thebath, cooled, dried and weighed at room temperature. The weight of the bulb filled with thevapor was 36.127 g; the weight of the empty (evacuated) bulb was 35.427 g; the bulb'svolume was 200.0 mL; room temperature was 25°C; and the barometric pressure was720 mm Hg. Calculate the molecular weight of the organic liquid.

Question
Asked Nov 6, 2019
6. In the molecular weight determination by the Dumas method, as illustrated below,
several grams of an organic liquid were drawn into the bulb. The bulb was then immersed in
a water bath at 87 C and kept there until all the liquid was vaporized and the air in the bulb
was replaced by the vapor. The tip was then sealed shut and the bulb removed from the
bath, cooled, dried and weighed at room temperature. The weight of the bulb filled with the
vapor was 36.127 g; the weight of the empty (evacuated) bulb was 35.427 g; the bulb's
volume was 200.0 mL; room temperature was 25°C; and the barometric pressure was
720 mm Hg. Calculate the molecular weight of the organic liquid.
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6. In the molecular weight determination by the Dumas method, as illustrated below, several grams of an organic liquid were drawn into the bulb. The bulb was then immersed in a water bath at 87 C and kept there until all the liquid was vaporized and the air in the bulb was replaced by the vapor. The tip was then sealed shut and the bulb removed from the bath, cooled, dried and weighed at room temperature. The weight of the bulb filled with the vapor was 36.127 g; the weight of the empty (evacuated) bulb was 35.427 g; the bulb's volume was 200.0 mL; room temperature was 25°C; and the barometric pressure was 720 mm Hg. Calculate the molecular weight of the organic liquid.

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Expert Answer

Step 1

The mass of the bulb filled with vapor was 36.127 g;

The mass of the empty (evacuated) bulb was 35.427 g; its volume was 200.0 mL; room temperature is 25C, and the barometric pressure was 720 mmHg.

Step 2

The mass of the organic chem in the bul (bulb filled with vapor) 36.127g- mass of the empty (evacuated) bulb 35.427g = 0.7 g of mass.


P = 720 mmHg which determines the value of R to be used

R is the ideal gas constant

R = 62.3636711 m³·mmHg/mol·K

200mL =0.2L

Step 3

Use the ideal gas law PV = nRT sub the values from above, unknown is n, all others are known.

n=PV/RT

&nb...

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