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Balancing Moles Unit

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Valerie Henderson

on 4 February 2016

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Transcript of Balancing Moles Unit

23
Chemquest 30 Introduction
to Moles

one atomic mass unit (amu) is equal to 1.6611 x 10 grams.
The Match-up Method
___CO + ____ NO = ____CO + ____N
Chemistry
Unit 4
Balancing Moles



-Moles
-Balancing Equations
-Types of Reactions

Coefficient
The coefficient is the number in front of the compound.
Steps:
1. Determine the number of each atom on the left and right.
What is the number called in front of this compound? (what do we call it in math)
2 NaCl
coefficient
"Wholey Mole-y Notes"
Objective: To practice counting things you cannot see.
Standard:
Topic Molar Definition
Benchmark SC.CH.5.1 Explain how the quantity of one mole is set (e.g. defining one mole of carbon 12 atoms to have a mass of exactly 12 grams) and describe its properties (e.g. one mole is 6.02 x 10 particles (atoms or molecules))
Essential Question:
1. What is a mole and why is it used?
Notes: "Balance is Important"
Standard:
SC.CH.5.4 Write balanced equations to describe chemical reactions.
SWBAT write and balance chemical equations to represent synthesis, decomposition, single replacement and double replacement reactions.
What is a chemical reaction?
What is a chemical
equation?
Chemical equations are used to describe ___________________.
chemical reactions
Chemical equations have 3 parts:
1. Reactants and Products
2. Descriptors
3. Atoms on the left = atoms on the right.
s= solid
g = gas
l = liquid
(see descriptors reference)
aka BFF 3.0
(balanced)
Types of Reactions:
1. Combustion
organic compound
What's organic?
has carbon!
+
oxygen
=
CO
+
H O
2
2
combine something with carbon (organic) with oxygen to produce carbon dioxide and water
gives off heat
endo- or exo- thermic?
exothermic!
Otto cycle = four-stroke combustion cycle
1. piston starts @ the top and moves down to let the engine take in a cylinder-full of air and gasoline.
what gas is in air?
oxygen (O )
2
gas is hydro-carbon
= intake stroke
2. Piston moves back up to compress this fuel/air mixture (add pressure). Compression (adding pressure) makes the combustion reaction more powerful.
3. When the piston reaches
the top of its stroke, the spark plug emits a spark to ignite the gasoline. The gasoline charge in the cylinder explodes (combustion), driving the piston down.
4. Once the piston hits the bottom of its stroke, the exhaust valve opens and the exhaust leaves the cylinder.
What is in exhaust?
CO
CO
2
Nitrogen dioxide
NO
2
(this comes from the catalytic converter in your exhaust system breaking down heavier nitrogen gases.)
carbon monoxide
carbon dioxide
Types of Reactions
2. Synthesis
Two or more simple compounds combine to form a more complicated one.
which stock name?
iron (III)
Fe
O
2-
--
--
--
+++
+++
3+
Types of Reactions
3. Decomposition
opposite of synthesis
One substance breaks down into two or more simpler substances.
sodium azide
N
2
(g)
+
Na
The nitrogen gas produced inflates the bag so your face doesn't hit the wheel.
Types of Reactions
5. Double Replacement
Baking soda (NaHCO ) reacts with acidic substances (HA) in cake batter

NaHCO + HA --> Na A + H(HCO )
3
3
3
The anions and cations of two different molecules switch places.
Types of Reactions
4. Single Replacement
One atom trades places with another element in a compound.
thermite = used in welding
Fe O
2
3
Al
(s)
+
Mix 76.3% iron oxide with 27.3% aluminum powder to make thermite.


To make the military version Thermate create a mixture of 68.7% thermite, 29.0% barium nitrate, sulfur 2.0%, and dextrin 0.3%.
Al O
2
3
Fe
+
2
2
can cut concrete and steel @ the same time!
Summary time!
How do you write your summary?
Answer the essential questions!
Creating your own questions for better learning:
QFT:
Question Formation Technique
Ground Rules
Q-Focus:
Warm-up 4.1 "Creating Questions for Better Learning"
From last class' QFT, please write one higher level thinking question. (
You can use your Depth of Knowledge Levels Reference
)
Please be prepared to share.
Please share your higher level question with your group.
Please choose one person to be the scribe.
The scribe will write down everyone's question.
We will post these questions and they will help to guide our learning of balancing equations.
Today's exit ticket asks you to write:
If your higher level thinking question does not get answered today, you may use it on the exit ticket.
Return of the Lego Atoms
Please put this aside to complete at the end of class.
For questions 1-4, refer to Lego Atoms
For 4 a. b. c .
ionic vs covalent foldable
warm-up 3.1
You may find it helpful to color to color the boxes indicate for each element. These are the colors that are standardized to represent the elements.
Return of the Lego Atoms

6.
Please work with your partner to use the legos to
create
a model the equation for number 6.
*Hint: for Na, remember what type of element it is. What is the name for the group it is in.
Cl
2
Compare the Cl you made to #4 on lego atoms. Can you apply the concept of the subscript we learned to improve this reactant (Cl )
2
2
7. Discussion Question:
With your group, please discuss:
The
connection
between the Law of Conservation of Matter and balancing equations.
The Law of Conservation of Mass states that matter can be changed from one form into another, mixtures can be separated or made, and pure substances can be decomposed, but the total amount of mass remains constant.
We can state this important law in another way. The total mass of the universe is constant within measurable limits; whenever matter undergoes a change, the total mass of the products of the change is, within measurable limits, the same as the total mass of the reactants.
http://chem.wisc.edu/deptfiles/genchem/sstutorial/Text1/Tx14/tx14.html
source:
For numbers 9 a. b. c.
Return of the Lego Atoms
Work with your partner (and table group when necessary) to
create
models using the legos of each chemical reaction listed.
Now that you have made the connection between the Law of Conservation of Mass (matter) and balancing equations...
With your partner, please go back to number 6 and critique your lego model.

When you have finished your critique and revised (if necessary) your lego model, please raise your hand.
Once you have created your lego model (
BEFORE drawing it
), please raise your hand.
2
2
C:
N:
O:

C:
N:
O:

1
1
1
2
2
= 2
x2
2
3
x2
= 4
2
x2
=2
2
x2
= 2
x2
=2
x2
4
1
+ 1
How?
subscript!
2. To have the same number of each atom on the left and the right, you can only change the ________. NEVER change the subscripts!
coefficient
balancing tips:
keep polyatomics together. (If same on both sides)
1.
__ Fe + __ H SO __Fe (SO ) + __ H
2
4
2
4
3
2
Fe
H
SO
2
4
Fe
H
SO
2
4
1
1
1
2
1
3
3
x 3
x 3
= 3
= 3
x 3
= 3
3
2
x 2
= 2
Use fractions.
some balancing tips:
__ C H + __ O __ H O + __ CO
2
6
2
2
2
C:
H:
O:
C:
H:
O:
2
6
2
1
2
2
3
x 3
x 2
= 6
2
x 2
= 2
1
x3
+
= 3
7
5
How can you get 7 Os on the other side?
fraction!
7
2
x
7
2
= 7
Can't leave the fraction in equation!
How do you get rid of fractions?
What is a fraction? (What does the horizontal line mean?)
divide!
part: whole
ratio
If you multiply the entire equation by the denominator, fraction is gone.
(
)
2
6
7
4
2
Counting Things:
When you buy eggs you usually ask for a _____ eggs.
dozen
You know that one dozen of any item is ____.
12
Why is it useful to use units like a dozen or a ream?
Paper is not packaged by the dozen. Paper is packaged by a ream. A ream of paper has 500 sheets.
A dozen and a ream are counting many things.
Instead of counting by the individual egg, they can be counted by the dozen so they are packaged by groups of 12.
How can eggs be packed?
dozen
2 dozen
half dozen
A ream is more efficient than counting by sheet. You can pack multiple reams in a box and label the box as having 10 reams.
What determines how many items should make up a particular unit?
How much is in a standard package.
duodecim
= 12 in latin
12 months/yr
12 cycles of moon in 1 yr
(much is historically based)
If you were asked to design a new unit to count something, what would you consider when choosing how many items should included in your own unit?
Avogadro's Number:
6.022 x 10
23
atoms
The mole is a counting unit. It is used to count out a given number of ______.
-24
(12.011 amu) x (1.6611x10 g) = 1.9951x10
-24
-23
amu
12.011 g
1.9951 x 10
23
g
1 atom
=
6.0201 x 10
23
atoms
2. How many carbon atoms does it take to equal 12.011 grams?
3.
According to the periodic table, a single phosphorus atom has a mass of 30.973 amu. What is the mass of a single phosphorus atom in grams?
(30.973 amu) x (1.6611x10 g) = 5.1449x10
1 amu
-24
-23
4. How many phosphorous atoms does it take to equal 30.973 grams?
30.973g
1 atom
5. Compare your answers to questions 2 and a 4.
They are both approximately the same.

Therefore, it takes about 6.02x10 atoms of carbon to equal the atomic mass in grams and it takes 6.02x10 atoms of phosphorus to equal its atomic
mass in grams.
23
23
g
Real-Life Applications:
How does an airbag work?
An impact equivalent to hitting a brick wall at 10-12 miles per hour triggers the decomposition of sodium azide to produce solid sodium and nitrogen gas.
What happens in a decomposition reaction?
How many reactants?

How many products?
1
2
One reactant breaks down into 2 or more products
Step 1: What are the reactants and products?
Solid sodium azide breaks down into solid sodium and nitrogen gas.
sodium azide
sodium
Nitrogen gas
+
NaN
3
Na
(s)
+
N
2
(g)
Step 2: Write the skeleton equation.
reactant
products
(chemical formulas without balancing the equation)
Step 3: Balance the skeleton equation.
NaN
3
Na
+
N
2
(s)
(s)
(g)
Na:
N:
Na:
N:
1
3
1
2
2
x 2
x2
=
=
2
6
3
x3
= 6
x 2
= 2
2
Water in Space
Real Life Applications:
Dealing with cellular respiration products
*remember cellular respiration is combustion reaction so the products are CO and H O
2
2
Humans = animals. They generate energy for their cells using cellular respiration.
The carbon dioxide produced by humans has to be removed from the space shuttle because a build-up could be deadly.
CO is removed from the air using canisters of lithium hydroxide (lithium hydroxide scrubbers).
2
The reaction of carbon dioxide with lithium hydroxide produces lithium carbonate and water.
Step 1: Determine the products, reactants.
carbon dioxide
lithium hydroxide*
lithium carbonate*
water
+
+
reactants
products
Step 2: Use the word equation to write the skeleton equation and determine the reaction type.
CO
LiOH
Li
CO
+
3
2-
Li CO
2
3
+
--
+
Li CO
2
3
H O
2
+
+
Li
OH
+
-
+
-
LiOH
*(BFF 2.0)
2
C:
O:
Li:
H:
C:
O:
Li:
H:
1
2 + 1 = 3
1
1
1
3 + 1 = 4
2
2
2
x2 = 2
x2 = 2
Word Equations to Balanced Equations
How many grams in 1 amu?
1 amu = 1.6611 x 10
-24
What are the two conversion factors?
1 amu
1.6611 x 10
-24
1.6611 x 10
-24
1 amu
According to the periodic table, a single carbon atom has a mass of 12.011 amu. What isthe mass of a single carbon atom in grams?
amu
grams
OR you can write it using criss cross applesauce:
12.011 g
1 atom
1.9951 x 10
23
x
=
6.0201 x 10
23
atoms
g
x
g
5.1449 x 10
-23
=
6.0201 x 10 atoms
23
g
5. Compare your answers to questions 2 and 4.
Answers to questions 2 and 4 are the same. Both answers are Avogadro's number (one mole).
What do you get when you cut an avocado into 6.02 x 10 pieces?
23
g
g
g
Return of the Lego Atoms
In Lego atoms, what did individual Lego bricks represent? ______________
atoms
An atom can be called a _____________ (so can a molecule because it functions as 1 unit.
particle
What is used to represent the number of atoms in the molecule?
subscript
_________
When you connected the Lego bricks, we said they were connected by what? ___________ bond
chemical
a. An ___________ bond forms between ________ cations and __________anions.
ionic
positive
negative
b. A _________bond forms between ____________ and ___________.
covalent
nonmetal
nonmetal
c. A __________ bond forms between a metal and a metal.
metallic
6. Please use the Legos and the index cards with + and = sign to represent the following equation:
Na + Cl NaCl
2
=
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