Stoich Test News

We are still planning on having the test in Chem Honors tomorrow, but we are aware that  some of you are deeply affected by today’s tragic events and are not in any condition to either study or take the test, which is completely understandable. Therefore, Ms. Fisher and I have decided to leave it to your discretion – if you feel you cannot prepare and take the test tomorrow, just tell us and you may use the period for study. If you feel you are able, then take the test in class.

For those of you who need to delay taking the test, we will ask that you take the test on Monday during the PLC time after the school day. We hope that this is a fair accommodation to those of you who need a little more time to deal with this loss.

Learning Targets

These are a bit rough – more of an outline – but posting them here in case they might be of some use.

Learning Targets

Solutions Test Today!

Be sure and schedule a makeup time ASAP – tomorrow or Monday is best so it’s still fresh in your mind!

Tomorrow we start talking about gases. If you want to get a head start, begin looking over Chapter 5!

A few more helpful precipitate prediction sites

Hey – here are a few practice sites for the solubility rules and reaction writing since Mr. Guch doesn’t seem to have any of those.

Quizlet – Flashcard-type practice that asks you to decide if a compound is soluble or not. The instructions aren’t great (in the sense that there aren’t any) – type YES if it is soluble and type NO if it is insoluble (makes ppt).

Reaction practice – it doesn’t come with a key, but I made one! ppt practice key

More solubility practice – A few compounds at the end of this page to determine soluble/insoluble. Warning, the key is literally 2 lines below the questions so if you don’t want to be tipped off, scroll down SLOWLY.

Remember you can always have a friend print their Webassign for you to get some new problems – at this point the key will be showing!

The Mole!

Introduced the concept of the mole, a unit used in chemistry. Like a dozen, it is a word that means a specific number of things. A mole is equal to 6.022 x 10²³ basic particles, such as atoms, molecules, ions, or electrons. So a mole of copper metal contains 6.022 x 10²³ atoms of copper. A mole of water contains 6.022 x 10²³ molecules of water.

The mole is the number of atoms of C-12 that have a mass of exactly 12 grams – the same value for the mass of a single C-12 atom in amu. Since the masses on the periodic table are relative, that means that a mole of an element  weighs, in grams, the atomic mass of that element from the periodic table. This is known as the “molar mass” – the mass of one mole. The mass of a mole of a compound can be found by adding the molar masses of the elements that the compound is made of.

So, a mole of hydrogen atoms weighs 1.008 g. A mole of oxygen atoms weighs 16.00 g. A mole of water, which is comprised of 2 H and one O, would weigh 2(1.008) + 16.00 = 18.02 g.

The molar mass of a covalent (molecular) compound is sometimes referred to as the molecular mass or molecular weight. These terms mean the same thing as molar mass – the mass of one mole of the substance.

Naming Map

If this works…here is a map/flowchart for deciding how to name a compound…to get a formula just work backwards.

Naming Review and Study Tips

Test Tuesday!

Be sure and check out the Helpful Tools and Links page (bottom of right column) – there is a link to an overview of naming rules and organic naming rules there which you may find helpful.

Some general tips:

1. Make sure you know the rules for each kind of naming (ionic, covalent, acids, organic).
2. Be able to identify the kind of compound, so you know which set of rules to apply.
3. Just like learning a new language, practice! practice! practice! is the best way to get good at it. Try extra problems at the end of Chapter 3 (odd answers in back of book), or try a friend’s WebAssign if they have different problems than you do.
4. The Mr. Guch’s website (on my links page under General) has many practice worksheets with answer keys to use!

Organic Compounds

Last type of naming – organic compounds.

Compounds based on chains of carbons are classified as organic. Usually, the first element in the formula will be carbon, followed by hydrogen and possibly other elements. Compounds containing only carbon and hydrogen are called hydrocarbons and are named using a prefix for the number of carbons in the chain, and a suffix for the type of bonds between the carbons.

Test on Naming Tuesday 11/3!

Acids

Quiz on polyatomic ions today, followed by acid naming – if you missed it you must make it up tomorrow! (If you’re still out tomorrow you’ll be taking a different quiz).

Learned the rules for naming acids. If the acid does not contain oxygen, it is named hydro_______ic acid, where the root of the other element/ion in the compound goes in the middle. Ex: HCl = hydrochloric acid.

If the acid contains oxygen, then determine the polyatomic ion in the name. If the polyatomic name ends in -ate, change it to -ic and add “acid.” If the polyatomic name ends in -ite, change it to -ous and add “acid.” Ex: HNO₃ –> NO₃^- is nitrate –> nitric acid. HNO₂ –> NO₂^- is nitrite –> nitrous acid.

Using Polyatomics

Tips!

Remember that you need parenthesis around the polyatomic ion’s formula if there’s more than one of them in the compound (to show there’s several of the entire group), but there are no parenthesis if there’s only one of them or around monatomic ions. In particular, watch out for hydroxide and cyanide….people forget the parenthesis on these two ions most frequently!!

Don’t forget, Webassign is due 10/30!