QUESTION 3 In the Dumas experiment, you measure the following data: massgas + fl

Question

QUESTION 3 In the Dumas experiment, you measure the following data: massgas + flask= 1434316g masscold water + flask= 385.75g density of water= 0.9987g/mL mass empty flask = 142.56g Temperature of boiling water when the system is sealed 105.3°C A) Calculate the molar mass of the gas. Te experiment, we weighed the empty flask" when it was full of air. This is usually a minor error in an experiment, because we don't remove the air after an experiment, so the effect in other experiments is negligible. However, since we removed all of the air in the flask and replaced it with our gaseous unknown, it has a large effect on the molar mass calculations. Correct for the air in the 'empty flask measurement as follows: B) Use the density of air at room temperature (1.225g/L) to determine the mass of air contained in the flask. C) Subtract the mass of air from your original "empty flask" mass. D) Compute the molar mass of the gas using the real mass of the empty flask. Attach File Browse My Computer Click Save and Submit to save and submit. Click Save All Answers te sue all m

Explanation / Answer

Dumas method for molar mass determination

A) from the given data

mass of gas (m) = 143.4316 - 142.56 = 0.8716 g

mass of water = 385.75 - 142.56 = 243.19 g

volume of flask (V) = 243.19 g/0.9987 g/ml = 243.51 ml = 0.24351 L

Temperature (T) = 105.3 oC + 273 = 378.3 K

Pressure (P) = 1 atm

R = gas constant

molar mass of gas = mRT/PV

                              = 0.8716 x 0.08206 x 378.3/1 x 0.24351

                              = 111.114 g/mol

B) density of air = 1.225 g/L

mass of air in flask = volume x density

                               = 0.24351 L x 1.225 g/L

                               = 0.30 g

C) subtracting air mass from flask mass = 142.56 - 0.30 = 142.26 g

D) new values

mass of gas (m) = 143.4316 - 142.26 = 1.1716 g

mass of water = 385.75 - 142.26 = 243.49 g

volume of flask (V) = 243.49 g/0.9987 g/ml = 243.81 ml = 0.24381 L

molar mass of gas = mRT/PV

                              = 1.1716 x 0.08206 x 378.3/1 x 0.24381

                              = 149.175 g/mol

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