Author Topic: 100%(benzene) = ???moles/dm^3 ??????  (Read 3934 times)

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pink_dust_angel

  • Guest
100%(benzene) = ???moles/dm^3 ??????
« on: June 08, 2004, 05:48:00 PM »
ok say swim has some 100% pure benzene, what is the molarity of this?
how does 1 work out the molarity of a pure substance knowing only the number of moles present?
swim only knows the following calcs:
   Moles= mass(g)/molar mass
   Moles= volume(dm^3) x moles/dm^3
this leaves swim with 2 unknowns (if swim only knows how many moles are present)

Rhodium

  • Guest
You need to look up the density and molar mass
« Reply #1 on: June 08, 2004, 06:30:00 PM »
Molarity = Moles/dm3
Density = Grams/dm3
Molar mass = Grams/Mole

Molarity = molar mass/density


carbocation

  • Guest
calculations
« Reply #2 on: June 08, 2004, 06:38:00 PM »
okay, the relative molecular weight (M/R) of benzene= 78. Therefore 78g= 1 mole
A 1M benzene solution= 78g benzene per dm3.
The density of benzene= 0.8765 g/cm3.
1 dm3 benzene= 876.5 g.
in 1dm3 pure benzene there is 11.23 moles (876.5/78). Therefore the molarity of 100% benzene= 11.23 moles/dm3

pink_dust_angel

  • Guest
thnk u very much ppl now swim will be able to...
« Reply #3 on: June 08, 2004, 07:16:00 PM »
thnk u very much ppl now swim will be able to dream his dream
;D