WORKING OUR WAY TO STOICHIOMETRY…
Hello Students!
In our approach to continue your academic progress, I am providing you with information about the topics we were going to cover in class this semester. I highly suggest you read the notes and watch the videos I am including in my blog.
Please, practice the problems presented in the videos and notes to check your understanding on the subjects presented to you. You have my email address and can always check with me through it.
These assignments are an introduction to STOICHIOMETRY. However, we will also need to cover “Balancing Equations” before getting in full into STOICHIOMETRY.
For now, you will need a good understanding of what a “MOLE” is and how to calculate “MOLAR MASS.”
THE MOLE CONCEPT
NOTES:
Moles
The mole is the "counting unit" used by chemists to indicate the number of atoms, ions, molecules, or formula units present in a particular chemical sample. The mole is similar to other counting units that you've used before....pair (2), dozen (12), and gross (144). One mole of a compound contains Avogadro's number (6.022 x 1023) of molecules (molecular compound) or formula units (ionic compound).
Chemists defined a mole as the amount of atoms that are in exactly 12 grams of carbon-12, which is Avogadro’s number!
CONCEPTS:
· One mole represents Avogrado’s number of atoms, ions, molecules (covalent bond) or formula units (ionic bond). This is a huge number: 6.022 x 1023
· One mole equals the amount of atoms in 12 grams of Carbon-12
o If you weight 12 grams of Carbon-12 it will contain ONE MOLE which means that it will also contain 6.022 x 1023 atoms because ONE MOLE has 6.022 x 1023atoms
o 12 g C-12 = 1 mole = 6.022 x 1023 atoms
1 mole of Fe contains 6.022 x 1023 atoms 1 mole of Li contains 6.022 x 1023atoms
1 mole of Ca contains 6.022 x 1023 atoms 1 mole of Al contains 6.022 x 1023atoms
Read until you get to EXAMPLE 1: CONVERTING MASS TO MOLES We’ll get to that later)
MOLES VIDEOS:
Tyler DeWitt is a favorite of mine and so is Boozeman. Feel free to Youtube for any videos regarding the concept of Moles. These are just suggestions I think will help you to better understand this very important chemical concept.
HOW TO CALCULATE MOLAR MASS
NOTES:
http://www.occc.edu/kmbailey/Chem1115Tutorials/Stoichiometry_Molar_Mass.htm
Formula Weight (FW)
Use to calculate the molar massof ionic compounds (ionic bond). The molar mass is based on the atomic weight of each atom (this is the numerical equivalent to the atomic mass unit or “amu” you find in the periodic table).
The units you will use are grams/moles or moles/grams instead of “amu.” You must use the periodic table in order to calculate molar masses since you need to find the “amu” of each atom and change the units from “amu” to grams/mole.
Sum of the atomic weights for the atoms in a chemical formula
· The formula weight of calcium chloride, CaCl2, would be
Ca:1(40.08 g) + Cl: 2(35.45 g) The formula unit has ONE atom of Ca and TWO atoms Cl. Notice I am using the units of grams instead of “amu.”
Don’t forget to multiply the amu by the subscript which tells you how many atoms of each kind you have. Again, in this formula, chlorine has TWO atoms and you must multiple the “amu” you find in the periodic table by 2 in order to get the correct mass for Cl2
Adding the masses of Ca and Cl2 you get 110.98 grams/ mole of CaCl2
This means that there are 110.98 grams in ONE mole of CaCl2
Molecular Weight (MW) Use to calculate the molar massof molecules (covalent bond)
• Sum of the atomic weights of the atoms in a molecule. The process to calculate the molar mass of MW is the same as for FW as explained above
• For the molecule ethane, C2H6, the molecular weight would be
C: 2(12.01 g) + H: 6(1.008 g)
Molar mass of ethane is 30.07 g/mole. One mole of ethane contains 30.07 grams
PRACTICE:
VIDEOS:
Tyler DeWitt is a favorite of mine and so is Boozeman. Feel free to Youtube for any videos regarding the concept of Molar Mass. These are just suggestions I think will help you to better understand this very important chemical concept.
