Chem Spring 2008

DTCC PreRN · Mar 13, 2008

Took my second CHM 131 test last night. (made a 91 on my 1st one) 3 hours long and finished 2 out of 3 pages. Thank goodness I wasn't the only one. We're being tested on electronegitivity, oxidation/reduction, oxidation states, balanceing reactions, molecular conversion, naming compounds, polarity, naming formulas, limiting reactants and the list goes on...

We're supposed to finish the test after lab on Monday. Please pray for me.

AlishiaRN77 · Mar 13, 2008

thanks alli, i just need to copy that information and take it with me to my exam! i wish i could get away with it. here's another one for you (or anyone else)... is there an "easy" way, or even just at really good way... to remember solubility rules?? oh my goodness. between chemistry and a&p my brain is turning to mush!

you are very welcome! i hope it made it a little easier for you. as for solubility rules, here's a list that i found on a website.

1. salts containing group i elements are soluble (li+, na+, k+, cs+, rb+). exceptions to this rule are rare. salts containing the ammonium ion (nh4+) are also soluble.

2. salts containing nitrate ion (no3-) are generally soluble.

3. salts containing cl -, br -, i - are generally soluble. important exceptions to this rule are halide salts of ag+, pb2+, and (hg2)2+. thus, agcl, pbbr2, and hg2cl2 are all insoluble.

4. most silver salts are insoluble. agno3 and ag(c2h3o2) are common soluble salts of silver; virtually anything else is insoluble.

5. most sulfate salts are soluble. important exceptions to this rule include baso4, pbso4, ag2so4 and srso4 .

6. most hydroxide salts are only slightly soluble. hydroxide salts of group i elements are soluble. hydroxide salts of group ii elements (ca, sr, and ba) are slightly soluble. hydroxide salts of transition metals and al3+ are insoluble. thus, fe(oh)3, al(oh)3, co(oh)2 are not soluble.

7. most sulfides of transition metals are highly insoluble. thus, cds, fes, zns, ag2s are all insoluble. orificenic, antimony, bismuth, and lead sulfides are also insoluble.

8. carbonates are frequently insoluble. group ii carbonates (ca, sr, and ba) are insoluble. some other insoluble carbonates include feco3 and pbco3.

9. chromates are frequently insoluble. examples: pbcro4, bacro4

10. phosphates are frequently insoluble. examples: ca3(po4)2, ag2po4

11. fluorides are frequently insoluble. examples: baf2, mgf2 pbf2.

not sure if this is what you were looking for but thought it was worth a shot. they listed this in an easy way.

now to make it much easier....that i don't know..lol. good luck!

tlaspires2rn · Mar 13, 2008

Oh my gosh, I just got home from taking my 2nd chemistry exam. I hate it when they make 3 problems (really HARD multi step problems), worth 30 points out of 100. It makes you feel horrible if you don't think you got them correct, because you've immediately got less than a C if you missed those 3. I made a 96 on our first exam, so this one really threw me. Then, to top it off, this one girl finished the whole exam in less than 10 minutes and went bouncing out of the room. I'm sitting there thinking that either I'm really just not getting this stuff or for some people it just comes a whole lot easier. Yes, I thought well maybe she just gave up and turned it in....I don't think so. You could tell by the look on her proud and happy face :icon_roll Oh well, we'll pray for a BIG curve!!! :banghead:

itsa307 · Mar 14, 2008

Took my second CHM 131 test last night. (made a 91 on my 1st one) 3 hours long and finished 2 out of 3 pages. Thank goodness I wasn't the only one. We're being tested on electronegitivity, oxidation/reduction, oxidation states, balanceing reactions, molecular conversion, naming compounds, polarity, naming formulas, limiting reactants and the list goes on...
We're supposed to finish the test after lab on Monday. Please pray for me.

We'll have our 2nd exam in a few weeks on the same stuff and it's going to be incredibley hard for me. I don't get the whole molecular conversion stuff and now we're doing some other conversion pv=nrt stuff that I'm having trouble with. I think I may be losing my B soon. I'm just hoping to pass this class. And to top it off my college has decided to make CNA a pre-req to getting into the nursing program so I have to figure out when I'll be fitting that into my schedule prior to applying. I don't know how I'm going to be able to do all this without it taking forever. I can't afford it and I just don't have the time without taking it away from the kids. I just don't know....

itsa307 · Mar 16, 2008

Gas Laws anyone? This is what we're working on now. Our teacher will provide us with the basic formula on tests and then we'll have to decide where to put what. How do you remember what goes where? Like for Boyles V2=P1V1/P2 or the reverse for P? Is there a trick to remember all these laws? Thanks!

AtomicWoman · Mar 16, 2008

Gas Laws anyone? This is what we're working on now. Our teacher will provide us with the basic formula on tests and then we'll have to decide where to put what. How do you remember what goes where? Like for Boyles V2=P1V1/P2 or the reverse for P? Is there a trick to remember all these laws? Thanks!

The way I learned gas laws is really easy. The combined gas equation is:

V1P1T2 = V2P2T1 (I love that equation, because usually it's explained with temperature in the denominator; here everything is straight multiplication.)

If you can remember that one equation, you can do any Boyle's Law, Charles' Law or Gay-Lussac's Law problem. The trick to remembering the equation is that TEMPERATURE is the only one of the 3 out of sequence. So it's V1P1T2 on the left and V2P2T1 on the right. If you can remember that, you've got it made. If you have problems remembering that, you can always use the combined gas equation, where all the 1s are on one side and all the 2s are on the other, but then you have to remember to divide by temperature. Either way works, but I find the straight multiplication equation easiest. [The other way would be (V1P1)/T1 = (V2P2)/T2 ]

If you're doing a problem where P is constant, then it drops out of the equation, and you're left with V1T2 = V2T1. If you're doing one where T is constant, then you're left with V1P1 = V2P2. And if you're doing one where V is constant, then you're left with P1T2 = P2T1.

You simply fill in your unknowns and divide. You will be missing ONE piece of information. So if P2 is unknown, it's: (V1P1T2) / (V2T1). The side of equation where all 3 pieces of info are known is ALWAYS the numerator; the side of the equation where you are looking for the unknown ALWAYS becomes the denominator, and your answer is the piece of information that was unknown.

The most important key to doing gas law problems is to IMMEDIATELY convert any temperature into Kelvins. The second you look at the problem, CROSS OUT the Celsius or Fahrenheit temperature. The combined gas law equations and Boyle's equation, etc. ONLY work if temperature is in Kelvins. Also, make sure your pressure units are the same on both sides of the equation: atm, mm Hg, Pascals, etc.

The other key is practice, practice, practice. After a while, you won't care if it's a Charles' Law problem or Boyle's or Gay-Lussac's. You'll just go filling in the equation and solve for the unknown.

Here's a link to Mr. Guch's explanation of the gas laws.

http://misterguch.brinkster.net/gaslaws.html

Notice he uses the equation where you have temperature in the denominator, so that will show you what I was talking about. Also, he has an explanation of the Ideal Gas Law, which is somewhat different and used in a different situation.

Best of luck!

itsa307 · Mar 18, 2008

Well my quiz last nite went really well. I got a B! I should've gotten an A but a made a dumb mistake on the first question by not reading it properly. Our quizes are timed and the extra pressure from the time limit really messes with me but I'm happy with the B. Tomorrow is our last lab before break and then when we come back it's exam 2. This one will be harder but I'm just going to have to study more! Thanks for the help!

itsa307 · Mar 19, 2008

I just found out I actually did get an A! The question I got wrong was only worth 10pts so I got a 90%! YEAH!!! Sorry, it's my first one on his quizzes other than the first safety quiz...

Sapana · Mar 19, 2008

Is anyone offering help for organic chem. I need help really bad.

itsa307 · Mar 19, 2008

Is anyone offering help for organic chem. I need help really bad.

Sorry I haven't started organic yet but maybe someone else has...

Sapana · Mar 19, 2008

Thanks itsa for the quick reply. I just joined this forum and i am struggling with my school. Could you be able to tell me how this works.. is there a different group doing ochem?

AlishiaRN77 · Mar 19, 2008

well my quiz last nite went really well. i got a b! i should've gotten an a but a made a dumb mistake on the first question by not reading it properly. our quizes are timed and the extra pressure from the time limit really messes with me but i'm happy with the b. tomorrow is our last lab before break and then when we come back it's exam 2. this one will be harder but i'm just going to have to study more! thanks for the help!

i just found out i actually did get an a! the question i got wrong was only worth 10pts so i got a 90%! yeah!!! sorry, it's my first one on his quizzes other than the first safety quiz...

congrats on your a!!!! yeah!!! doesn't it feel good knowing that all the studing pays off!! very happy for you... :yeah: :)

we just got done with spring break and had class last night. we were handed another quiz right away. i think i did ok....it was all on nomenclature. so we shall see...fun fun.

thanks itsa for the quick reply. i just joined this forum and i am struggling with my school. could you be able to tell me how this works.. is there a different group doing ochem?

there is a website that has chemistry help on all levels. go to www.mychemtutor.com. hopefully they will be able to help. i haven't taken organic chem since the early 90's.....so i'm not sure if i would be able to help you, i'm sorry.