BrightRed

Drats. I dug through the summer homework packet for chemistry a week ago (I know it's kind of late) and we're required to memorize:

-solubility rules
-predicting reactions (5 of them)
-common ions and their charges
-polyatomic ions

I've been trying to get the solubility rules and reactions down for the past week. Reaction rules weren't so bad, but I couldn't even get the first row of solubility rules down without frying my brain.

All that "except", "slightly soluble" stuff... arrgh. And it looks like someone banged on their keyboard to produce a random array of letters.

How did you guys do it?

Newjack88

That's all pretty easy. If you understand it, you won't really have to memorize all of these things. You'll eventually be able to reason your way through it.

gloriousnoise

To make it easier to remember, consider anything that says "slightly soluble", "maginally soluble", etc, as insoluble, because the extent of dissociation is so small it's hardly worth mentioning. And for the 'excepts', you may notice that there are certain trends and repetitions among the exceptions - Pb, Ag, Ba, etc. are repeated several times, if I remember correctly (took the AP test earlier this year.) The easiest way to remember is by doing practice problems, so don't worry, they'll start sticking eventually.

arnoc

Solubility rules are usually pretty simple. ALL alkali metal compounds are soluble, as are ALL ammonium compounds. ALL nitrates and acetates are soluble. The exceptions are generally easy to work out when you have a few base ones memorized.

dragonscale333

My teacher uses mnemonics a lot.
For solubility, we had Nag-Sag (something about teachers nagging people not to sag)
N - nitrate
A - acetate
G - G1 (Group 1, aka alkaline metals)
S - sulfates (except PMS and CastroBear (calcium, strontium, barium))
A - ammonium
G - G17 (halogens EXCEPT PMS, which are lead(Pb), mercury, and silver))

I think some of these are slightly soluble, but I forgot those.

As for the common polyatomic ions, my teacher had us only memorize the common ones (borate, carbonate, nitrate, phosphate, sulfate, and chlorate). If you look on a periodic table, you can easily find the elements elements in a pattern. The charges go 3-2-1, 3-2-1, respectively. The number of oxygen in the ions is 3-3-3, 4-4-3.

I hope this helps! It kind of did for me earlier in the year.

arnoc

The -ates are definitely not comprehensively "the common polyatomic ions." What happened to the -ites? Also, acetate is a major ion, as are hydroxide, ammonia, and ammonium.

dragonscale333

For the -ites, hypo-s, and per-s, you just tack them on to the -ate and do the math. Acetate, hydroxide, and ammonium are all 1 in charge; all you have to do is remember that ammonium is the only major +1 ion.

BrightRed

Very helpful. Thanks!

Any more suggestions, keep them coming!

arnoc

Simple reaction prediction is generally.. simple.

A + B -> AB (synthesis)
A + BX -> AX + B (single replacement)
AX + BY -> AY + BX (double replacement)
A + OH- -> H2O (neutralization)
A + O2 -> CO2 + H2O (combustion)

What you'll eventually have to do is be able to predict products, which honestly gets really terrible if your teacher doesn't specifically go over it as its own topic. You'll deal with topics like heating metal oxides, putting metal oxides in water solution, mixing ionic solutions, adding acids and bases to compounds, etc.

The most useful site I've ever come across for reaction prediction is Practice

marie03

sounds exactly like my summer packet!

BrightRed

^^ We have to memorize those too, like:
ammonia + acid -> ammonium salt
and the likes. We have 9 of these.

It's turning out to be some summer.

cuthalion42

Last year in AP Chem we had the same things, and all of us pretty much screamed as well. but the thing is, if your teacher gives you the kind of practice you should have, by the end these rules will bu stuck in your head forever. We just had to do so many examples that we memorized the rules along the way without even trying, so to speak.

Eevn so, it is useful to know them beforehand

ditto

I'm sure it all seems like a lot (I thought I'd never get solubility rules right). What really helped me was: 1.) practicing with them (just getting acquainted with the general trends and names and whatnot) 2.) flashcards - those help a LOT; I reviewed them before each test and it certainly helped me not lose points on the silly, little details.
Good luck - you'll get them eventually!

chibistar6

Wow. You guys have to memorize all this stuff without having taken the class yet? We just kindof memorized things as we went along...haha we didn't even get to memorizing solubility rules until 2 weeks before the AP test.
Trust me, concepts build off of one another, so it will get much easier as you progress through the year and learn to actually use what you've memorized. Right now, memorizing all that unfamiliar stuff is kind of...scary xD