Chemistry Fall 2008

CracklinRose · Oct 1, 2008

Congrats....that's great news.

I have been missing from this thread....busy w/school and taking care of a terminally ill family member unexpectedly....sigh!

I am doing well s far but am afraid of my first lab exam next Mon....I am unprepared for that, plus we are moving over the wknd....so much to do......Chem lecture, I am carrying an A though.

BellasMommyOBRN · Oct 2, 2008

my exact issue :)

my biggest issue with chemistry is that i just don't care about it... :chuckle the work itself isn't actually that difficult, it just doesn't intrigue me, i don't see the point, i don't care about valence electrons, i don't care how the ph has changed to this beaker of water when we add 5 drops of the solution, i don't care about chromatography or precipitate... i just don't care... which makes it a little hard to sit focused through the class!

phoenixRisin9 · Oct 2, 2008

Hey CracklinRose, sounds like the month of August I had....good luck with everything!

smellyacres, BSN, RN · Oct 2, 2008

My Chemistry professor rocks! I know I didn't get A for my first reading quiz but I know I won't give up! This is the first week of school so next it will be A! Now I know what to expect so I will do it fine! :) And... chemistry is not so hard as I expect :)
Biology...that is another story...but I won't give up too :)

Oh man! I totally agree! Chemistry is GREAT, but i can not for the life of me seem to do well in biology. I mean, I have a B, but i've gotten a B in biology since sixth grade when you begin science. Its to much memorization about things i do not care about. OH WELL, I try my best! Keep it up!

msdeannah · Oct 9, 2008

Hey guys.

I got a 94 on my last test. But now I think my A streak is coming to an end. I am totally lost and we have a test again on tuesday. We are predicting chemical reactions (solid, water, redox, and combustion) and balancing equations. I got the balancing, the precipitates I'm ok on and even water for that matter (even though thats a little shaky) can someone please direct me to a tutorial for help with redox. :bluecry1: . I'm seriously freaking out.

BusyMomof5 · Oct 9, 2008

Hi Everyone

Well so far I have really enjoyed my Chem class but tomorrow is our first test so I guess I'll see how it's sinking in. I started back to school Spring quarter and this quarter is the first quarter I'm taking two classes and I'm in way over my head because the "other class" is Statistics...online. So, I have 5 kids under 10, have been out of school 14 years, and I'm taking Chemistry w/ a lab and Statistics. Taking it online means teaching yourself from a text which I am finding out is apparently not my strong point. :banghead:

As you all know, Math moves very fast and I'm having a tough time keeping up! I've tried connecting w/ others in my online class but I'm surprised at how many students aren't interested in working w/ others..I guess it's that whole pre-med competitive thing. ? :scrying:

Luckily we are on the quarter system so the pain is only 12 weeks long. I have been looking around AN and don't see many threads for Statistics classes. I think that I'm missing it. Does anyone have any tips or any advice on where I can go to get some?

I forgot to say that the reason I'm taking 2 classes this quarter is that my CC added Stats to the list of pre-reqs in June. I had to "double" up on one quarter and I didn't want to double it up w/ A&P I, A&PII, or Microbiology. Plus they only accept applications one time a year so I would have to wait another year to apply to NS. In other words, I had no choice. I doubt I'd be as stressed as I am if I was taking Stats/Chem separately.

Any ideas? Words of wisdom? Any would be much appreciated. :redbeathe:redbeathe

AtomicWoman · Oct 9, 2008

Hey guys.
I got a 94 on my last test. But now I think my A streak is coming to an end. I am totally lost and we have a test again on tuesday. We are predicting chemical reactions (solid, water, redox, and combustion) and balancing equations. I got the balancing, the precipitates I'm ok on and even water for that matter (even though thats a little shaky) can someone please direct me to a tutorial for help with redox. . I'm seriously freaking out.

Here's redox on one of my favorite chem study sites:

http://www.chemguide.co.uk/inorganic/redoxmenu.html#top

This guy has a wonderful way to explain everything in chemistry as simply as possible. You may or may not need the section on writing redox half-equations, but the rest of his redox info may help you.

One of my other fave sites is chemreview.net. Here's their redox info:

http://www.chemreview.net/confirm11d.htm

Click on the link in point #3 on that page.

Hope this helps!

brismama · Oct 11, 2008

need help with limiting reagents. the book i have sucks and i cant seem to find any online websites that explain it pretty well. but i did try. can someone who understands it please let me know if this is right? :banghead:

q: if 20 grams of hydrogen reacts with 48 g of nitrogen to produce 15 grams of ammonia (nh3). (note: write a balanced equation before you proceed) 3h2 + n2 à 2nh3

what is the limiting reagent? nitrogen (see the workout below)

moles of h2- 3.307

moles of n2 - 1.71

what is the theoretical yield of the product in moles and grams?

1.713 mol n2 x 28.020 g n2/1 mol n2 = 47.998 gn2

what is the percent yield?

30g/47.998 g =.625 x 100% = 62.50%

any help is appreciated!!!

AtomicWoman · Oct 11, 2008

need help with limiting reagents. the book i have sucks and i cant seem to find any online websites that explain it pretty well. but i did try. can someone who understands it please let me know if this is right?
q: if 20 grams of hydrogen reacts with 48 g of nitrogen to produce 15 grams of ammonia (nh3). (note: write a balanced equation before you proceed) 3h2 + n2 à 2nh3
what is the limiting reagent? nitrogen (see the workout below)
moles of h2- 3.307
moles of n2 - 1.71
what is the theoretical yield of the product in moles and grams?
1.713 mol n2 x 28.020 g n2/1 mol n2 = 47.998 gn2
what is the percent yield?
30g/47.998 g =.625 x 100% = 62.50%
any help is appreciated!!!

i haven't had time to work out the entire problem yet, but there are a couple of problems:

(1) you have more than 3.307 moles of h2. i mole of h2 is 2.016 grams (1.008 x 2). so you have nearly 10 moles of h2. you did the moles of n2 correctly.

(2) when they ask you for the theoretical yield of the product, you look at the right-hand side of the equation. so they are asking you how much nh3 (ammonia) will be produced.

(3) you correctly identified the limiting reagent as n2, but i'm not sure you arrived at the answer in a way that will help you in future problems. you always need to look at the ratio of the reactants. for every mole of h2, you need 1/3 of a mole of n2. (or, for every mole of n2, you need 3 moles of h2. same thing.) you have about 10 moles of hydrogen, but only 1.71 moles of nitrogen. if they were perfectly balanced, you'd have (1.71 x 3 = 5.13) moles of hydrogen. so you have a large excess of hydrogen, meaning there's more hydrogen hanging around waiting to react with nitrogen. if you have an excess of hydrogen, you have a deficit of nitrogen and of course, nitrogen then becomes the limiting reagent.

(4) figuring out your theoretical yield of ammonia again involves looking at the ratios, but this time bearing in mind that you only have 1.71 moles of nitrogen. what's the largest number of moles of nh3 possible? your balanced equation tells you you will get 2 x 1.71 moles (3.42) of ammonia, max. then you can convert that to grams of ammonia.

you're on the right track, you just need to do enough of them so you can think them through quickly. also, there are a couple of methods to solving them systematically, so if your teacher prefers you use one method or another, go with that method.

one of my favorite chem sites may also help you:

http://www.chemreview.net/chem8-10molesstoich.pdf

go to page 57 of the .pdf, or p. 192 of the page numbers at the bottom of the page. they have a nice, clear explanation of limiting reactants/reagents.

good luck!

msdeannah · Oct 13, 2008

Ok so my test is tomorrow. I'm in a much better place, althogh I still get tripped up writing equations and their subscripts correctly. So I'm going to practice that all night long since that makes all the difference in balancing the equations. Thanks for all of your help guys.

MAFDC08 · Oct 20, 2008

Hi everyone,

I'm struggling with an online chem practice quiz problem and welcome any insight.

Are there any valence electrons a cov coumpound such as nitrogen pentachloride?

My reasoning is that since it is a cov compound it's octet is satisfied. Any thoughts...

Thanks!

PreRN Katie · Oct 20, 2008

Hi everyone,
I'm struggling with an online chem practice quiz problem and welcome any insight.
Are there any valence electrons a cov coumpound such as nitrogen pentachloride?
My reasoning is that since it is a cov compound it's octet is satisfied. Any thoughts...
Thanks!

I would think the octet is satisfied as well, since in a covalent compound the elements "share" the electrons. But I could definitely be wrong. Good luck!