1. Notes #3:
STP
WCHS Chemistry

2. So far… only 1 way to count molecules
Moles = How many molecules
ONLY for:
PURE solids, liquids & gases (compounds & elements)
Moles = Mass FW

3. MOLES OF A GAS STP = Standard Temperature & Pressure
“Perfect world” conditions (always for us!) :)
Standard Temp = 0o C
Standard Pressure = 1 atm
IMPORTANT!
The volume of 1.00 mole of ANY gas under STP is 22.4 Liters!

4. All take up the same amount of space (volume) !
EXAMPLES
1 mole Helium (He) vs. 1 mole Nitrogen (N2) vs. 1 mole SF6
All take up the same amount of space (volume) !
Think of this like a parking lot…
There are 602 sextillion parking spaces…
Only 602 sextillion cars can fit, but the cars can be all different sizes

5. All take up the same amount of space (volume) !
1 mole Helium (He) mole Nitrogen (N2) mole SF6
Volume of 22.4 Liters Volume of 22.4 Liters Volume of 22.4 Liters
But no matter what, 1 mole of any gas ALWAYS has a volume of 22.4 Liters!!!

6. Moles of = volume in Liters gas at STP 22.4
NEW FORMULA!
Moles of = volume in Liters
gas at STP
Like a universal formula weight! :)

7. To go from mL to L, MOVE DECIMAL 3 times to LEFT!
QUICK REFRESHER
To go from mL to L, MOVE DECIMAL 3 times to LEFT!
1475. mL mL mL
1.475 L
0.056 L L
2 Things to Remember:
Don’t do any rounding after converting!
Number & unit must match. Ex: 0.17 L, 170 mL

8. RECAP! 2 EQUATIONS FOR FINDING MOLES
Be careful!
Are we talking about a mass (grams)?
Moles = mass FW
Are we talking about a gas at STP (liters)?
Moles of = volume in Liters
gas at STP

9. QUICK REFRESHER ON MOLES
1 mole = 602 sextilltion molecules
HOW WE COUNT MOLECULES!!!! Na P → Na3P 3 Na P Na Na P Na
6 Na
P →
2 Na3P Na P Na Na P Na P Na Na Na P Na
ONCE YOU KNOW MOLES OF ONE THING, YOU KNOW MOLES OF EVERYTHING