12 4 conversions review
TRANSCRIPT
Launch: 12/4 Grab your binder and immediately take a seat!
Place homework (practice questions), binder paper, and a pen/pencil on your desk.
Today’s Objective: I can convert between grams and atoms using both molecular mass and Avogadro’s number as a conversion factors
Tonight’s HW: Relax!
Launch 12/4 Take the next three minutes to look over you notes
(11/23 to 12/1) and prepare for the quiz.
Warning: If people are not taking advantage of the study time, we will start the quiz immediately!
Launch 12/4 1. How did Avogadro define the mole?
Launch 12/4 2. Which conversion factor would need to be used to
convert gramsmoles? a. Avogadro’s number b. 6.02 X 1023 atoms/mole c. Molecular mass
d. Atomic mass
Launch 12/4 3. Which conversion factor would need to be used to
convert atomsmoles? Why?
Launch 12/4 3. How many grams of H2 are there in 8.08g of H2?
Announcements Quiz on Friday
The mole Conversions
Unit exam in 2 weeks
How many atoms? – Part II Mr. Heffner 12/1/09
How many atoms? Conversion factors…
are used to convert one unit to another unit
? grams 1 mole
..or particles, or molecules
Molar Mass Avogadro’s #
? grams/mole 6.02 X 1023 atoms/mole
Grams Moles Atoms Moles
6.02 X 1023 atoms 1 mole
1 mole ? grams
1 mole 6.02 X 1023 atoms
sum of atomic masses
How many atoms? What if we want to convert grams atoms?
Need to use both conversion factors!
How many atoms? There is a 3-step process for conversions:
1. Write down the starting unit and look at the ending unit. 2. Write the conversion factor with the starting units on the
bottom. If grams, start with molar mass
If atoms (or particles, or molecules), start with Avogadro’s #
3. Cancel like terms and multiply across the top and bottom.
Example #1 How many atoms are there in 12.01 grams of carbon (C)?
Step #1: Write down the starting unit and look at the ending unit.
12.01 grams
How many atoms are there in 12.01 grams of carbon (C)?
Step #2: Write the conversion factor with the starting units on the bottom.
1 mol 12.01 g
Example #1
12.01 g X =6.02 X 1023 atoms 1 mol
X
Start with molecular
mass
Then use Avogadro’s #
How many atoms are there in 12.01 grams of carbon (C)?
Step #3: Cancel like terms and multiply across the top and bottom
1 mol 12.01 g
Example #1
12.01 g X =6.02 X 1023 atoms 1 mol
X
=1 X 6.02 X 1023 atoms 1
=6.02 X 1023 atoms
Ignore
Example #3 How many grams of CH4 are there in 12.04 X 1023 molecules?
Step #1: Write down the starting unit and look at the ending unit.
12.04 X 1023 molecules
How many grams of CH4 are there in 12.04 X 1023 molecules?
Step #2: Write the conversion factor with the starting units on the bottom.
16.05 g 1 mol
Example #3
12.04 X 1023 molecules X =1 mol 6.02 X 1023 molecules
X
Start with Avogadro’s #
Then use molecular
mass
How many grams of CH4 are there in 12.04 X 1023 molecules?
Step #3: Cancel like terms and multiply across the top and bottom
16.05 g 1 mol
Example #3
12.04 X 1023 molecules X =1 mol 6.02 X 1023 molecules
X
=12.04 X 1 X 16.05 g 6.02 X 1
=32.10 g 2 X 16.05 g =
Example #2 How many atoms are there in 16.00 grams of O2?
Step #1: Write down the starting unit and look at the ending unit.
16.00 grams
How many atoms are there in 16.00 grams of O2?
Step #2: Write the conversion factor with the starting units on the bottom.
1 mol 32.00 g
Example #2
16.00 g X =6.02 X 1023 atoms 1 mol
X
Start with molecular
mass
Then use Avogadro’s #
How many atoms are there in 16.00 grams of O2?
Step #3: Cancel like terms and multiply across the top and bottom
1 mol 32.00 g
Example #2
16.00g X =6.02 X 1023 atoms 1 mol
X
=16.00 X 6.02 X 1023 atoms 32.00 X 1
=3.01 X 1023 atoms
Ignore
.5 X 6.02 X 1023 atoms =
Whiteboards Work in pairs
Trade-off marker every question
You have 60 seconds to solve the question Show all of your work! Don’t forget units!
Lift board only when prompted
How many atoms are there in 8.00 grams of helium (He) ?
How many molecules are there in 4.04 grams of H2?
What is the mass (in grams) of 6.02 X 1023 particles
of gold (Au)?
How many grams does 3.01 X 1023 molecules
of HCl weight?
Practice Questions Practice question worksheet
Exit Slip 1. Which conversion factor would need to be used to
convert between gramsmoles? a. Avogadro’s number b. 6.02 X 1023 atoms/mole c. Molecular mass
d. Atomic weight
Exit Slip 2. Which conversion factor would need to be used to
convert grams into atoms? a. Avogadro’s number b. Atomic weight c. Molecular mass
d. both a & c
Exit Slip 3. Which of the following correctly shows how to convert
64.00g of O2 to atoms?
a. 32.00g X
b. 64.00g X
c. 64.00g X X
d. 64.00 g X X
6.02 X 1023 atoms 32.00g
1 mole 32.00 g
6.02 X 1023 atoms 1 mole
1 mole 32.00 g
1 atoms 32.00 moles
1 mole 6.02 X 1023 g
Exit Slip 4. How many atoms of nitrogen (N) are there in 14.01g?
a. 3.01 X 1023 atoms b. 6.02 X 1023 atoms
c. 9.03 X 1023 atoms d. 1.204 X 1024 atoms
Exit Slip 5. How many grams does 12.04 X 1023 molecules of
H2O weigh? a. 9.01g b. 18.02g c. 27.03g
d. 36.04g
Homework Finish practice questions
Study for Friday’s Quiz!