Homework Help: Chemistry

Posted by Diana on Thursday, May 21, 2009 at 4:39pm.

#1) The Lewis structure of PF3 shows that central phosphorus atom has ___ nonbonding and ___ bonding electron pairs.

#2) How many equivalent resonance forms can be drawn for CO3^-2? (carbon is the central atom)

#3) The bond angle in NF3 is slightly less than ___?

#4) Sample of gas (1.3mol) occupies ____L at 22 Celcius and 2.5 atm.

Chemistry - DrBob222, Thursday, May 21, 2009 at 4:44pm
I would be interested in knowing what you think about these questions and why? We are not in the habit of doing all of the homework. Show what you have done on a problem and we can help you through it.
Chemistry - Diana, Thursday, May 21, 2009 at 4:47pm
I am trying to study for my final exam. I am just trying to do my review packet and i just want to see if i am getting them correct.
but what i got was

1) 3,3
2) 2
3) 120
4) idk how to do that one.
Chemistry - DrBob222, Thursday, May 21, 2009 at 5:04pm
For PF3, I think P has 1 non-bonding pair and 3 bonding pairs. Here is a site that gives the Lewis structure for PF3. PF3 is closer to the bottom of the page.
http://chemistry.alanearhart.org/Tutorials/Lewis/lewis-part1.html
Chemistry - DrBob222, Thursday, May 21, 2009 at 5:08pm
#2. For CO3^-2, I would think there are three equivalent structures. You MAY have meant two + the original (which makes 3) but equivalent means all of them. All of them are resonance forms of each other.
We can't draw these things on the board but here is a site that does a nice job.
http://www.chem.ucla.edu/~harding/tutorials/resonance/draw_res_str.html
Chemistry - DrBob222, Thursday, May 21, 2009 at 5:16pm
NF3, Lewis structure wise, looks much like PF3. The electronic geometry, therefore, is tetrahedral (1 lone pair, and 3 pairs of bonded electrons). [Four regions of high electron density gives a tetrahedral structure.] The lone pair occupies more space; therefore, the tetrahedral bond angle of 109^o is reduced somewhat. So I think the answer should be "slightly less than 109^o. Here is a site that talks about that.
http://answers.yahoo.com/question/index?qid=20061129055540AAOTWwD
Chemistry - DrBob222, Thursday, May 21, 2009 at 5:21pm
#4. First, note the correct spelling of celsius.
Use PV = nRT.
P is in atmospheres (2.5), V is the only unknown (in liters), n is the number of moles (1.3), R is the universal gas constant of 0.08205 L*atm/mol*K, and T is the temperature in Kelvin (273+22 = 295 K

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