Welcome to Chemistry!
Atoms, Molecules and Holy Mole(y)!
1
What is a mole anyway?
A mole is simply a convenient unit of measurement:
6.02 x 1023 anything!
Molar Mass: mass of one mole of a substance
What is the mass of one mole of vitamin C, C 6H8O6?
How many molecules are in one mole of C 6H8O6?
There are 6.02 x 10 23 molecules in a mole of ANY substance.
How many atoms of each element are in one molecule of C6H8O6?
2
Ready to think?
How many atoms of each element are in one mole of C 6H8O6 ?
Drumroll please...
1 mole of C6H8O6 contains 6.02 x 1023 molecules:
How can I better understand moles?
Imagine a Big Mac....
Bread 3Hamb2Pickle6
Now imagine a dozen big macs...
Mmmmmmmm...a dozen Big Macs
3
In a dozen Big Macs:
How many pieces of bread? How many hamburger patties? How many pickles? Don't Big Macs make you love chemistry?
What about atoms and molecules?
Once again think of a Big Mac...
Bread3Hamb2Pickle6
In one Big Mac molecules there are 3 bread atoms, 2 hamburger atoms, 6 pickle atoms.
Now what if you had 10 Big Mac molecules?
You would have ____ bread atoms, ____ hamburger atoms, ____ pickle atoms
4
What if you had 4.26 x 1022 Big Mac molecules?
(That's A LOT of Big Macs...)
How many bread atoms?
How many hamburger patty atoms?
How many pickle atoms?
Working with mass, molar mass and moles
Remember: n (moles) = m (mass of substance, g)
mm (molar mass, g/mol)
Example: How many moles are in 13.42 g of water (H 2O)?
5
Adding in atoms and molecules:
How many molecules are present in 12.48 g of CH 4?
One last example:
You have 23.96 g of C2H6. How many moles are present? How many molecules?
How many carbon atoms?
How many hydrogen atoms?
6
What about all that STOICHIOMETRY stuff?
Stoichiometry allows us to determine quantities reacted or produced using the ratio of coefficients.
Ex.
What mass of water is produced when 37.5 g of oxygen are reacted in the following equation? How many molecules is that?
2 H2 + O2
2 H2O
Another example:
What mass of propane is required to produce 65.8 g of carbon dioxide in the following reaction? How many molecules is that? How many hydrogen atoms are in those molecules?
C3H8 + 5 O2
3 CO2 +
4 H2O
7
Do I really need to know all those chemical names?
Yup. BUT, you can use a reference table to help you figure out the molecular formulas using valence values.
What is the molecular formula for:
1. magnesium chloride
2. sulfur trioxide
3. aluminum bromide 4. dinitrogen pentoxide
Radicals too...
1. potassium phosphate:
2. sodium carbonate:
3. calcium nitrate: 8
What are these called?
1. BeCl 2
2. LiF
3. Mg3(PO4)2
4. AgNO 3
Write out and balance the following equation:
Sodium reacts with water to form sodium hydroxide and hydrogen gas.
9
Write the following equation in words:
2 Na3PO4 +
3 Ca(NO3)2
6 NaNO3 +
Ca3(PO4)2
Don't forget about the diatomic gases!
I Have No Bright Or Clever Friends
I2 H2
N2
Br2
O2
Cl2
F2
10