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 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.

Hydrates

Ionic compounds that can trap water in their crystalline structure are called hydrates. A term is added following the formula or name of the compound to indicate that it is trapping water, and to show the ratio of trapped water molecules to the ions in the compound.

Add “•n H₂O” after a formula, where “n” is a whole number giving the number of water molecules per unit of the compound: CuSO₄•5 H₂O.

Add “___hydrate” after a name using a prefix to indicate the ratio of water molecules per unit compound: copper(II) sulfate pentahydrate.

Polyatomic Ions

Recap of transition metal naming. Introduced polyatomic ions. Just like vocabulary in a foreign language, these need to be memorized. Click on the link below for the table of ions that need to be memorized for this year.

polyatomics

Quiz on Polyatomic Ions Wednesday 10/28!!

Attached to this post is a Powerpoint polyatomic Jeopardy game (I hope)!

Polyatomic Jeopardy

Practice and Transition Metals

Practiced some naming using the rules determined yesterday, then looked at examples of names for ionic compounds including both representative group and transition metals. Determined what the purpose of the roman numeral in the name for the transition metals is.

New Unit: Naming

Today we start our next unit, chemical naming. The class determined the basic rules for naming binary (two-element) compounds.

Unit 3 Test

Took test for Unit 3 today. Please see me ASAP if you missed it to schedule a makeup!

Chromatography Lab, Day 2

Today we took measurements and calculated Rf for our pigments. Lab books were turned back in at the end of class.

Reminder! There is a WebAssign up that’s due next Tuesday! You can do questions 4, 5,  and 8 now based on what we have covered in class so far. The remainder of the assignment will be based on what we discuss over the next few days.

Unit 2 test on Wednesday 10/7!