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.

 1 mole = 6.02 x 10 23 particles. This does not change.
 The number of particles in 1 mole is called Avogadro’s number

 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.
Answer 26.98 g/mol
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 NaHCO
3
= 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 NaHCO
3
= 84 g/mol
23 g x 1
23 g
+
1 g x 1
1 g +
12 g x 1
12 g
+
16 g x 3
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
Unknown: # moles
Conversion: 1 mol/12 g
Set up: 24 g x 1 mol =
12 g
Answer: 2 mol
Given: 10 mol
Unknown: # g
Conversion: 197g/1 mol
Set up: 10 mol x 197 g =
Answer: 1970 g
1 mol
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 10 23 as a conversion factor to move between moles and particles.
Ex 1: Particles to Moles. How many moles is 1.20 x 10 24 atoms of carbon?
Given: 1.20 x 10 24 atoms
Unknown: # moles
Conversion: 1 mol/6.02 x 10 23 atoms
Set up: 1.20 x 10 24 atoms x 1 mol =
6.02 x 10 23 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 10 23 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 10 23 /1 mol
Set up: 10 mol x 6.02 x 10 23 atoms=
1 mol
Answer: 6.02 x 10 24 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