Molar Mass

Molar Mass, as you've probably guessed, is the mass of 1 mole of a substance!
 It can be determined from the atomic mass on the periodic table

It's measured in grams per mole or g/mol.
I like the way that it is described in this phrase:
The atomic weight of an element expressed in grams contains 1 mole of that element.

To determine the molar mass of a compound, find the mass of each element individually and add them!
For example

NO2.  N= 14 amu, so 14 g
           O= 16 amu, so 16 g

           14+2(16)= 46 g/mol

What is the molar mass of Ammonium Phosphate?
Ammonium Phosphate is (NH4)3PO4
N= 14g x 3 = 42 g

H= 1g x 12 = 12 g

P= 31 g

O= 16 g x 4 = 64 g
42 + 12 + 31 + 64 = 149 g

Converting between Moles and Mass

To convert between moles and mass we use molar mass as the conversion factor. Make sure to cancel the appropriate units!

Examples:
How many grams are there in 1.5 mol of O2?

We are trying to cancel out mol, and convert it into grams, so when converting, we will put mol on the bottom, and grams on the top.

1.5 mol O2 x                   g   =               g

                           1 mol

We have to find the molar mass of O2, in grams. O= 16     16 x 2 = 32.0 g

1.5 mol O2 x 32.0 g    = 48 g

                      1 mol

How many moles are present in Fe2O3?

115 g Fe2O3 x 1 mol  =           mol
                               g

Fe= 55.8 x 2 = 111.6

O= 16 x 3 = 48 g                 111.6 g + 48 g = 159.6 g   * at this point, don't worry about sig fig's!

115 g Fe2O3 x 1 mol       =   0.721 mol Fe2O3

                         159.6 g

Here's another kind, that has more super cool detective problem solving:

A compound is made up of phosphorous and chlorine. It is found to contain 0.200 mol and has a mass of 27.5 g. Determine the molar mass, and a possible formula for this compound.

molar mass = g      = 27.5  g      =  137.5 g/mol          

                     mol      0.200 mol

To get the formula, you just have to try out different masses off the periodic table, and the one that works in this case is PCl3!

I wonder what the molar mass of this is?

Chemistry Pun of the day:

Q: What weapon can you make from the Chemicals Potassium, Nickel and Iron?
A: KNiFe.

The MOLE

you may think that a mole is a small furry blind creature who lives underground and looks something like this.....
cute right?
but we're talking chemistry so its not as simple as all that. For us the mole is a number that represents a huge number of particles. 6.02* 1023 particles, to be exact. But why do we even need a number to represent particles? Couldn't we just weigh and measure individual particles?

Here's the problem: atoms, molecules, and other particles are really small.

ex.  Helium has an atomic mass of 4.0 atomic mass units, but how much does one helium atom weigh in grams? The answer is an incredibly small amount, not very practical for day to day calculations.

So to fix that, a really smart, really old guy came up with an answer. This guy's name was Amadeo Avagadro and he came up with this number in 1811!  Here's his head shot.

Avagadro said, what if  4.0 grams of Helium contains a number of atoms? And what if this number of atoms is constant for all elements and compounds, depending on their atomic mass? According to Avagadro, 12 grams of Carbon, 4 grams of Helium, and 11 grams of Sodium would each have 6.02*1023 atoms.

There are 3 different conversions we usually do with Avagadro's number.

1. A sample of sodium has 5.6*1026 atoms. How many moles of sodium is this?

      5.6*1026 x 1 mol           = 9.3 mol
                       6.02*1023

2. 15 moles of chlorine equals how many atoms?
 
     15 x   6.02*1023 = 9* 1024
               1 mol
3. Or the opposite of number 1, which is how many molecules are in 3.09 moles of NaCl?

   3.09 mol x 6.02*1023 = 1.86*1024
               1 mol

These are the 3 different conversions you might need to do with the Mole.

oh and here's another mole:

Naming Compounds

Okay so the most common system for naming compounds is IUPAC (unfortunately I do not remember what this stands for though). The compounds which we learned about are:

Ions

Multivalent Ions
Binary Ions
Polyatomic Ions

Molecular Compounds

Hydrates
and
Acids/Bases
Of course some of these have already been explained in previous blogs so i won't go over all of them, just the ones we did in class.

Multivalent Ions -elements that can form more than one ion (ie. Tin has a +4 and +2 charge)

Thus I will teach you how to differentiate which charge it is without using the roman numeral way (Tin(II)).

It's quite simple actually if you are using the larger charge you add -ic on to the end the smaller charge is -ous, easy right? Oh and you take off any other suffix's. So for example Manganous Oxide. MO. However some of the ions don't sound very good when you just add the ending on so of course there are a few exceptions for the rule such as:

Fer-Iron

Cupp-Copper

Mercur-Mercury

Stann-Tin

Aunn-Gold

Plumb-Lead 

And I'm sure someone will realize that Fe 2+ is Ferrous easily making a....
How funny......



Next up...
Hydrates

These are basically water molecules, there's water inside of the molecule, and said water can be released with heat.

Now what to call these things, just follow these simple steps and you will be able to name hydrates (it's a very useful skill I'm sure, or at least I think)

1)write the chemical formula

2)add a prefix to show the number of water molecules (prefix's such as mono-, di-,tri-....deca- etc.)

3)write hydrate after the prefix

It's very complex isn't it.

An example of this would be LiF-3H₂O which becomes Lithium Flouride Trihydrate

On to the next topic which is.....
Acids and Bases
(don't worry this one is very brief)
Basically an acid has Hydrogen in it you add -ic onto the end and put in the word acid afterwards, for example SCNH is Thiocyanatic Acid.
Bases are a cation and hydroxide, the only thing you do for this is add Hydroxide on to the end of the name, it's pretty easy, as easy as KOH results in Potassium Hydroxide.
However I must leave now because I am about to eat dinner

Drawing Electron Dot Diagrams

Electron Dot Diagrams, or Lewis Diagrams are... cool. Lemme show you why:

 LEWIS DIAGRAMS FOR SINGLE ATOMS

When Drawing Electron dot diagrams, the nucleus is represented by the atomic symbol.

For example:   Cl            Na

Determine the number of valence electrons (meaning the electrons in the outermost shell). Represent these by drawing that amount of dots around the chemical symbol.

Keep in mind:

*There are four orbitals (one on each side of the nucleus) and each can hold a max of 2e
*Each orbital gets 1e before they pair up

For Example:
Chlorine atom has 17 electrons.
2 in the first shell

8 in the next.

And 7 in the outer shell.

LEWIS DIAGRAMS FOR COMPOUNDS AND IONS

In covalent compounds, electrons are shared

First, determine the # of valence electrons for each atom int he molecule

Then, place atoms so that valence electrons are shared to fill each orbital

Examples:

Here is a VERY common covalent compound, H20... water!
Oxygen originally has 6 electrons, while each Hydrogen has 1 electron.

This totals up to 8 electrons, which fills up oxygen entirely as well as hydrogen (which only requires 2 electrons each, since its the first shell!)
 

And children, that's an example of how we share!

DOUBLE AND TRIPLE BONDS
Sometimes the only way covalent compounds can fill all their valence levels is if they share more than one electron (hence the double and triple!).
Examples

Carbon has 4 electrons, while each Oxygen atom has 6 in their valence shell.
This means that there's a lonely electron in each of the oxygens, and 2 lonely electrons in the carbon atom... so why not pair up and form a double bond?

IONIC COMPOUNDS

In Ionic compounds. electrons transfer from one element to another.
First, determine the number of valence electrons on the cation (positive ion) and move these to the anion (negative ion)
Then, draw [ brackets ] around the metal and non metal
-Write the charges outside the brackets
Par example,

Aluminum is a charge of +3, and Chlorine has a charge of -1. Since the electrons are moving onto the chlorine (we know this, since chlorine's negative), we only draw the electrons around the chlorine.
Remember to write the charges on the outside of the brackets!

POLYATOMIC IONS
First ,determine the # of valence electrons for each atom int he molecule

Then, subtract one electron for each positive charge OR add one electron for each negative charge
Example

CO3 -2

Carbon- 4 electrons

Oxygen- 6 electrons x 3 = 18 e

+2 electrons (because the charge is -2)

Isotopes and Atoms

Okay, sorry for the late post but here it is, isotopes and atoms. Let's start with the basic definition of an atom.
Atom-- the smallest unit of an element, having all the characteristics of that element
Simple right?
Now i realize that the scientific atom might not seem as interesting as this guy right away but it can be quite amazing. (but maybe not quite so much right now)
 
and now a couple formulas you need to know
Atomic Number = Number of Protons
Atomic Mass- Atomic Number = Number of Neutrons
Where to find these numbers you're wondering? Well you can find them right here.

The 6 in the upper left corner represents the Atomic Number
The =/-4 represents the charge (it's not particularly important for this though)
The C is the symbol for Carbon
The 12amu represents the mass (in atomic measuring units)






However not all atoms of the same element are identical some have a different mass these are called isotopes
An Isotope has the same Atomic Number as the atom it represents but a different mass.
For example
 This is a Carbon isotope. When writing isotopes you see the two numbers in front of the C, the top number is the mass number, the bottom is the atomic number. Same atomic but different mass number.
Easy right.
Thus we shall finish off with a couple of comics. On chemistry related and the other not so much.
 
Because running is really going to save you.