Hi can someone help me solve these 3 chem problems?

1. A chemist does not have access to a barometer, and therefore uses the value of 760 mm for the atmospheric pressure in a formula weight determination. Would the value of the formula weight be high, low, or the same as compared to your reported value; (which is 763 mm) calculated with the actual barometric pressure? Explain.


2) If the unknown liquid does not completely vaporize during the heating process, will the formula weight be too high, low, or the same?

3) a chemist is given an unknown liquid having a boiling point of 155 degress celsius. What changes would have to be made in the experimental proceudre to determine the formula weight of this compound? (Dumas determined the vapor density of numerous high boiling species and even some solids!)

thanks

Answer:
1. As I understand this, a known mass of a liquid is vaporized and the volume of gas (assumed ideal) is measured to determine the number of moles. The two equations that are used are the ideal gas: PV=nRT and the number of moles n = mass / formula weight (FW). Combined together these give: FW = (mass)RT/(PV).
Based on this equation, if a pressure is used that's lower than the actual, the FW will be higher (by 0.4%) than it should be.

2. Using the same equation but now comparing the effect of incomplete vaporization which is evident from the volume of gas evolved. If there is complete vaporization, the volume will be bigger and FW smaller. If there is incomplete vaporization, the volume of gas is smaller, and FW will be bigger than it should be.

3. I'm not sure what the experimental procedure was originally, but I can guess that heating to a higher temperature or heating at a reduced pressure (partial vacuum) is what needs to be done.

The answers post by the user, for information only, FunQA.com does not guarantee the right.



More Questions and Answers:
  • Calculate the molecular weight?
  • Why is water cycled around the engines of most cars, even though it can present a problem with rusting?
  • There is a professor from Indiana University at Bloomington?
  • Can you completely destroy water ? if it gets too hot it turns to steam , and too cold to ice ??
  • How is it that the structure of H20 give is the ability to dissolve so many different solutes.?
  • 2/3: challenge! for chem wiz only!?
  • In relation to the natural resource rubber, what are its sources, uses, and problems associated with its use??
  • Battery experiment - If I can't find zinc, which will act as my electrode, can I use a galvanized product?
  • How can you extract starch from vegetables, fruits, root crops?