Transcript U4 One Step Conversions

U4 One Step
Stoichiometry
Problems
Chemistry Ms. Boon 10.10-10.11
Catalyst
 Pick up the notes handout and answer the
following question at the top of the page:
 10 weeks have passed since the first day of
school. How many days have passed? How
do you know?
7 days = 1 week
10 weeks
X
7 days =
1 week
70 days
Objective

I can perform one-step stoichiometry
conversions using a worksheet, notes, and a
puzzle.

I can show my work and use units in all my
calculations.
Mini Review: What is the mole?
 The mole is a number we use to make counting
atoms, ions, and molecules much easier. The
mole allows scientists to count by weighing.
Think, Pair, Share: What is counting by weighing?
Imagine you work at a candy store and a customer asks
for 500 jelly beans. There is a long line and you do not
want to count 500 beans. But you have a scale. What
can you do?
Answer: Find the weight of one bean. Then multiply by
500. Finally, measure this mass of beans and it should
be 500 beans.
Mini Review: What is the mole?
1 mole = 6.02 x 1023 particles. This
does not change.
The number of particles in 1 mole is
called Avogadro’s number
THE MOLE -- Why?
Why is the mole useful to us as chemists??
Make a dot on your paper with your pencil.
Guess how many atoms of Carbon graphite are in
that dot.
25 million atoms in that tiny dot!
Mini Review: What is the mole?
 Molar mass and molecular weight are the mass in grams
of one mole of an element or compound.
 Different elements and compounds have different molar
masses or molecular weights.
Example 1: What is the
molar mass of aluminum?
Hint: The molar mass is the
same as the atomic mass,
just add “g” for grams.
Example 2: What is the
molecular weight of baking
soda? Hint: First find the
mass of each element, then
multiply by subscripts, then
add up the answers.
Answer 26.98 g/mol
Answer NaHCO3 = 84 g/mol
Mini Review: What is the mole?
Example 2: What is the molecular weight of baking
soda? Hint: First find the mass of each element, then
multiply by subscripts, then add up the answers.
Answer NaHCO3 = 84 g/mol
23 g
x1
23 g
+
1g
x1
1g
+
12 g
x1
12 g
+
16 g
x3
48 g
= 84 g/mol
5 minute - Quick Practice: Choose at least 2 molar
mass/molecular weight problems from your worksheet.
Stoichiometry Conversions Part 1: Grams to
Moles and Moles to Grams.
 Calculating the molar mass or molecular weight of a chemical reveals the mass
of one mole of that chemical. What if we are given more than one mole of a
substance? Or some random amount in grams? Use the molar mass or
molecular weight as a conversion factor to move between moles and grams.
Ex 1: Moles to Grams. How
many moles is 24 g of
carbon?
Ex 2: Grams to Moles. How
many grams is 10 moles of
Gold?
Given: 24 g
Given: 10 mol
Unknown: # moles
Unknown: # g
Conversion: 1 mol/12 g
Conversion: 197g/1 mol
Set up: 24 g x 1 mol =
Set up: 10 mol x 197 g =
12 g
1 mol
Answer: 2 mol
Answer: 1970 g
5 minute - Quick Practice: Choose at least 2 gram to mole
or mole to gram problems from your worksheet.
Stoichiometry Conversions Part 2: Particles to
Moles and Moles to Particles.
 Avogadro’s number allows us to determine the number of atoms, molecules,
or ions (generally particles) in a given sample. Use 1 mole = 6.02 x 1023 as
a conversion factor to move between moles and particles.
Ex 1: Particles to Moles. How many moles is 1.20 x 1024 atoms
of carbon?
Given: 1.20 x 1024 atoms
Unknown: # moles
Conversion: 1 mol/6.02 x 1023 atoms
Set up: 1.20 x 1024 atoms x 1 mol =
6.02 x 1023 atoms
Answer: 2 mol
Stoichiometry Conversions Part 2: Particles to
Moles and Moles to Particles.
 Avogadro’s number allows us to determine the number of atoms, molecules,
or ions (generally particles) in a given sample. Use 1 mole = 6.02 x 1023 as
a conversion factor to move between moles and particles.
Ex 2: Moles to Particles. How many atoms is 10 moles of
Gold?
Given: 10 mol
Unknown: # atoms
Conversion: 6.02 x 1023 /1 mol
Set up: 10 mol x 6.02 x 1023 atoms=
1 mol
Answer: 6.02 x 1024 atoms
5 minute - Quick Practice: Choose at least 2 particle
conversion problems from your worksheet.
Extra Special Bonus: Video Review –
Super Hero Science

How does the law of conservation of mass limit the size
of a super hero?

http://www.youtube.com/watch?v=fpV7DKwcqbk&list=P
LJicmE8fK0EjcBM04Tz0UvUTJ3utyYD1G
More Practice

See textbook p. 224-233

Try the sample problems on p. 228 and 229