Long but quick chemistry lab that I needconfirmation on answers?

Question

OK so I have this lab that went pretty quickand smooth and I have an online assessment that I needed to put allmy figures in. I am all complete but am having trouble with 1problems that the assessment is saying is wrong and I am lookingfor someone to verify or explain what I am doing incorrect.

Here were the steps of the lab and my findings:

Determining the molecular weight of Acetone:

Step 1: Obtain a Dumas bulb from the Equipment menu.

Step 2: Record the volume of the bulb in liters (volume is markedon bulb). .056L

Step 3: Record the mass the empty bulb using an electronic balance.50.g

Step 4: Place 20 ml of acetone into the bulb.

Step 5: Obtain a 600-ml beaker.

Step 6: Select Beaker and place about 500 ml of water into beakeror enough to cover neck of bulb.

Step 7: Combine bulb with beaker (using combine menu option).

Step 8: Obtain a hot plate from Equipment menu.

Step 9: Place combined Dumas bulb and beaker assembly onto hotplate.

Step 10: Turn on hot plate to maximum heating setting.

Step 11: Allow all acetone to boil away and wait 1-2 minutes beforeremoving bulb from beaker.

Step 12: After removing bulb from beaker, allow Dumas bulb to cooluntil acetone vapors have condensed (2-3 minutes).

Step 13: Weigh bulb and condensed vapor using an electronic scaleand record result. 50.1062g

Then the lab told me to use this info to answer the assessment:

(i) Volume of Dumas bulb (L): 56ml or .056L

(ii) Mass of empty Dumas bulb (g): 50g

(iii) Mass of Dumas bulb + condensed acetone (g):50.106

(iv) Mass of acetone gas required to fill bulb ((iii) - (ii)):.106

(v) Molecular weight of Acetone: Mass / n = Mass / (PV/RT) = (Mass*R *T) /(P * V) =.00183

Given:
Pressure: 1atm
Temperature: 373 Kelvin (boiling point of water)

Then Here was the question I needed to answer (which I am gettingnumber 5 incorrect):

1)Weight of empty Dumas flask=50g
2)Weight of acetone=? 15.714
3)Weight of liquid vapor after condensing=.106
4)Moles of acetone vapor based on ideal gas law=.00183
5)Calculated molecular weight of acetone based on experiment.58
6)%error from the theoretical molecular of acetone and theexperimental value.=which to me seems like there is a 0%error OK so I have this lab that went pretty quickand smooth and I have an online assessment that I needed to put allmy figures in. I am all complete but am having trouble with 1problems that the assessment is saying is wrong and I am lookingfor someone to verify or explain what I am doing incorrect.

Here were the steps of the lab and my findings:

Determining the molecular weight of Acetone:

Step 1: Obtain a Dumas bulb from the Equipment menu.

Step 2: Record the volume of the bulb in liters (volume is markedon bulb). .056L

Step 3: Record the mass the empty bulb using an electronic balance.50.g

Step 4: Place 20 ml of acetone into the bulb.

Step 5: Obtain a 600-ml beaker.

Step 6: Select Beaker and place about 500 ml of water into beakeror enough to cover neck of bulb.

Step 7: Combine bulb with beaker (using combine menu option).

Step 8: Obtain a hot plate from Equipment menu.

Step 9: Place combined Dumas bulb and beaker assembly onto hotplate.

Step 10: Turn on hot plate to maximum heating setting.

Step 11: Allow all acetone to boil away and wait 1-2 minutes beforeremoving bulb from beaker.

Step 12: After removing bulb from beaker, allow Dumas bulb to cooluntil acetone vapors have condensed (2-3 minutes).

Step 13: Weigh bulb and condensed vapor using an electronic scaleand record result. 50.1062g

Then the lab told me to use this info to answer the assessment:

(i) Volume of Dumas bulb (L): 56ml or .056L

(ii) Mass of empty Dumas bulb (g): 50g

(iii) Mass of Dumas bulb + condensed acetone (g):50.106

(iv) Mass of acetone gas required to fill bulb ((iii) - (ii)):.106

(v) Molecular weight of Acetone: Mass / n = Mass / (PV/RT) = (Mass*R *T) /(P * V) =.00183

Given:
Pressure: 1atm
Temperature: 373 Kelvin (boiling point of water)

Then Here was the question I needed to answer (which I am gettingnumber 5 incorrect):

1)Weight of empty Dumas flask=50g
2)Weight of acetone=? 15.714
3)Weight of liquid vapor after condensing=.106
4)Moles of acetone vapor based on ideal gas law=.00183
5)Calculated molecular weight of acetone based on experiment.58
6)%error from the theoretical molecular of acetone and theexperimental value.=which to me seems like there is a 0%error

Explanation / Answer

From the data you've given, I got Mass of acetone = 0.106g           { weight of filled bulb - weight of empty bulb} Volume of acetone = 0.056 L . Substituting in the gas equation, n = P V / RT mass/ molar mass = P V/ RT . Molar mass = mass * R * T / (P V)                   = 0.106 g * 0.0821 L-atm/molK. * 373K / (1 atm * 0.056 L)                   = 57.97 g/mol . Hope this helps.

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