Now, I do feel stupid asking for help with this, but I haven't had chemistry in almost 4 years.

The questions are:

1) How many moles of molecules and atoms are in a 5.1g sample of CH4? Use the atomic masses C=12, H=1
2) How many moles and grams of Carbon are present in 7g of C13H18O2? Use the the following atomic masses: C=12, H=1 O-16

Ok, for the these, I think I get it, but I am trying to figure out if I am understanding right...
3) If a proton moves away from another proton
4) Two electrons move toward one another
5) An electron moves away from a proton
6) Two sodium atoms move toward one another
7) A Cation moves toward an Anion
We have to tell if the energy increases, decreases or has no change.

Can whoever answers tell me HOW to work these problems out? That's more important in the long run, and my book is pretty unhelpful, as well as the teacher (ughh Dr. Orji).

thanks a bunch!

1/18/2006 7:47:02 PM

for #1 &2 use the formula
#of moles = mass/molar mass

the rule for #3,4,5,6&7 is, when two particles of the same sign come closer, energy increases,
that is because they are trying to get away from each other. and when two particles of
opposite signs move away from each other, energy also increases, because they are trying
to come closer.

Particles aim at lowering their energies, so whatever makes them act against their nature, energy
is gained.

Hope this helps

[Edited on January 18, 2006 at 8:23 PM. Reason : .]

1/18/2006 8:15:01 PM

oh sorry, didnt notice on #2 that you are trying to find the number of moles for Carbon only.
for that you gotta also take into mind that for every mole of C13H18O2, there is 13 moles of C

so 0.7gC13H18O2*(1mol C13H18O2/206gC13H18O2)*(13mol C/1molC13H18O2) gives you number
of moles of Carbon

and then, to find the mass of Carbon use the formula
moles = mass/molar mass

1/18/2006 8:33:31 PM

thanks SO much sharrami!

1/18/2006 8:49:58 PM

Go to SI. Your leader can make the course a ton easier (most of the time).

[Edited on January 19, 2006 at 1:45 AM. Reason : asdf]

1/19/2006 1:44:08 AM

I would go if all the session weren't when I have other classes, or after I've already driven back home to Durham for the day, where I live.

1/19/2006 1:48:37 AM

seriously i never had a chem class (i took cp in high school and i cheated the whole time)and i never had to resort to this. for the record i have a learning disability in this shit.

1/20/2006 12:27:33 AM