QUESTIONS 1. If an insufficient amount of liquid unknown had been used, how would this have...



1. If an insufficient amount of liquid unknown had been used, how would this have affected the value of the experimental molar mass?

2. What are the major sources of error in your determination of the molar mass?

3. If the flask were not wiped completely dry, how would this derived mass of the gas affect the molar mass?

4. Isobutyl alcohol has boiling point of 108 C. How would you modify the procedure used in this experiment to determine its molar mass?

Molar mass :

Molar mass is a stoichiometric property of a compound, which is defined as the ratio of actual mass to the number of moles.

Answer and Explanation:


1) If an insufficient amount of liquid unknown had been used the unknown will not occupy the whole container. In the equation to find the molar mass {eq}\dfrac{nRT}{PV} {/eq}, the volume will be greater than the actual volume of the unknown, thus leaving a molar mass that is less than the actual molar mass


2) Errors would occur probably from getting the weight of the vapor since we are subtracting (container + vapor) - empty container because the two values will be almost the same.

Another way determination by taking a glass tube, sealing the end in a burner, then heating it and blowing a good size, thin-walled bubble to use as the container. We should determine the volume of the bubble. We would have a pre-heated container to keep the bubble in that is kept in the hot bath or oven while getting it to the balance to minimize cooling en-route.

If the container cools during the time we get it from the heating source to the scale some vapor will condense into liquid and draw some air in affecting the weight.


3) If the flask were wet when weighed, it would make it appear as if the vapor was a lot heavier than it actually was which would mess up our calculations for molar mass.


4) Isobutyl alcohol has a boiling point higher than water, we can't use water as the hot-bath liquid; we could possibly add ethylene glycol to raise the Bp of the water, or use another liquid such as oil, etc.

Learn more about this topic:

What is Molar Mass? - Definition, Formula & Examples

from General Studies Science: Help & Review

Chapter 27 / Lesson 24

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