April 11, 2021, 04:58:55 AM
Forum Rules: Read This Before Posting


Topic: Determining Formula from Molecular mass?  (Read 1735 times)

0 Members and 1 Guest are viewing this topic.

Offline jennielynn_1980

  • Full Member
  • ****
  • Posts: 167
  • Mole Snacks: +8/-4
  • Gender: Female
Determining Formula from Molecular mass?
« on: September 23, 2011, 04:44:29 PM »
Hi everyone.  I have figured out most of this question but the last part is really getting me.  I haven't been in a chemistry class for awhile so I am a little rusty.  If someone could tell me what direction to think in that would be great :)

A sample of 2.14 g of a gaseous organofluorine compound occupies a volume of  2.00 L at 25.5 C and 30.2 kPa.  What is the molar mass of this compound and what is it's formula?

So using PV=nRT
n= (0.298atm)(2.00L)/(0.08205 L atm K-1 mol-1)(298.65 K)
  = 0.0243 mol

Then using M=m/n
M = 2.14g/0.0243 mol
    = 87.9 g/mol

So I determined the molar mass but now how do I get the formula?

Thanks :)

Offline Borek

  • Mr. pH
  • Administrator
  • Deity Member
  • *
  • Posts: 26398
  • Mole Snacks: +1718/-402
  • Gender: Male
  • I am known to be occasionally wrong.
    • Chembuddy
Re: Determining Formula from Molecular mass?
« Reply #1 on: September 23, 2011, 06:54:50 PM »
The only possible approach is by trial and error. Start with simple compounds (like CH3F) and see if they fit the molar mass.
ChemBuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titrations.info, pH-meter.info

Offline jennielynn_1980

  • Full Member
  • ****
  • Posts: 167
  • Mole Snacks: +8/-4
  • Gender: Female
Re: Determining Formula from Molecular mass?
« Reply #2 on: September 23, 2011, 07:00:06 PM »
Thank you Borek.  I was trying to figure out how to do a percentage my mass setup but I wasn't getting far. 

Sponsored Links