Chemical Equations and Balancing

Multiple Choice

In the equation, which part represents the word "yields" or "produces"?

• Li₂O

• +

• H₂O

• "-->"

• LiOH

Multiple Choice

The substances listed on the left side of a chemical equation are the

• Products

• Coefficients

• Reactants

Multiple Choice

$$C_2H_6\ +\ 5O_2\ \rightarrow\ 2CO_2\ +\ 3H_2O_2$$  
Given this chemical equation, what are the REACTANTS?

• $$C_2H_{6\ }and\ 5O_2$$  

• $$2CO_2\ and\ 3H_2O_2$$  

Multiple Choice

The substances listed on the right side of a chemical equation are the

• Yields

• Reactants

• Products

Multiple Choice

$$C_2H_6\ +\ 5O_2\ \rightarrow\ 2CO_2\ +\ 3H_2O_2$$  
Given this chemical equation, what are the PRODUCTS?

• $$C_2H_{6\ }and\ 5O_2$$  

• $$2CO_2\ and\ 3H_2O_2$$  

Multiple Choice

The coefficient in  3H₂O is

• 6
• 2
• 3
• 5

Multiple Choice

How many molecules of KNO₃ are shown?

• 1

• 2

• 3

• 4

Multiple Choice

What are the blue numbers called?

• oxidation numbers

• subscripts

• group numbers

• product numbers

Multiple Choice

How many Magnesiums are in this molecule?

$$Mg_3P_2$$  

• 4
• 1
• 2
• 3

Endothermic Reaction- a specific type of reaction where heat/energy goes IN
the system
Exothermic reaction- a specific type of reaction where heat/energy EXITS the
system
Chemical Energy- energy stored in chemical bonds of compounds and
molecules
Conservation of Energy- the total amount of energy before the reaction and
after the reaction stays the same!

● Reaction Rate- the rate (or time) at which reactants
change into products…how fast or slow the reaction is going

● Catalyst-these are used to speed up a reaction by lowering
the activation energy needed

○ Think of it like a tool (a spoon stirring up milk and
chocolate syrup!)...it helps, but isn’t used up!

​Body Break Time!!!

What if I said….

• If you also have me for another class

this semester, you’re getting a FREE
lab grade!!!

Is this fair??
• Of course not! Just as I must show

equality in the classroom, chemical
equations demand equality as well.

• Therefore, we have to have

BALANCED chemical equations!

•Chemical equations must be balanced to show the same
number of atoms on each side of the equation.
•We balance equations by placing coefficients.

Al + S Al2S3 Not Balanced

2Al + 3S Al2S3 Balanced

•Chemical equations must be balanced to show the same
number of atoms on each side of the equation.
•We balance equations by placing coefficients.

Al + S Al2S3Not Balanced

2Al + 3S Al2S3 Balanced

N2 + H2 NH3

Is this balanced?

N2 + 3H 2NH3

Is this balanced?

N2 + 3H2 2NH3

+

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H2 + Cl2

2 HCl

• In a chemical reaction, the total mass of the reactants equal
the total mass of the products.

• This is called the Law of Conservation of Mass

Multiple Choice

In chemical reactions, what does the law of conservation of mass mean?

• Matter is not created or destroyed.
• The total mass of the reactants is greater than the total mass of the products.
• The total mass of the reactants is less than the total mass of the products.
• Matter is not changed.
  

H2 + Cl2

2 HCl

• In a chemical reaction, the total mass of the reactants equal
the total mass of the products.

• This is called the Law of Conservation of Mass

H2 + Cl2

2 HCl

• In a chemical reaction, the total mass of the reactants equal
the total mass of the products.

• This is called the Law of Conservation of Mass

Multiple Choice

An oreo cookie weighs 20 grams.  It gets crushed into crumbs for a recipe.  How much do its crumbs weigh?

• 15 grams
• 25 grams
• 20 grams

Multiple Choice

The Law of Conservation of matter states that the total amount of matter ______________ after it undergoes change.

• disappears
• stays the same
• weighs less
• explodes

Practice Balancing Equations

next week! This is a preview

Steps For Balancing Chemical Equations

1.

Write the equation for the chemical reaction. Check for diatomic molecules!

H2 + Cl2 HCl

2.

Count the atoms of the elements in the reactants.

H2 + Cl2

2 atoms of H

2 atoms of Cl

3.

Count the atoms of the elements in the products.

HCl

1 atom of H 1 atom of Cl

4.

Change the coefficients to make the number of atoms of each element
equal on both sides of the equation.

5.

Write the coefficients in their lowest possible ratio.

H2 + Cl2 2HCl

6. Check your work.

Balancing Chemical Equations

What coefficients would we add to the equation below to balance it?

Al + Br2 AlBr

Balancing Chemical Equations

What coefficients would we add to the equation below to balance it?

Al + Br2 AlBr

​Al ?


Br ?

​Al ?


Br ?

Balancing Chemical Equations

What coefficients would we add to the equation below to balance it?

Al + Br2 AlBr

​Al 1


Br 2

​Al 1


Br 1

Balancing Chemical Equations

What coefficients would we add to the equation below to balance it?

Al + ?Br2 2AlBr

2

2,1,2

Fill in the Blanks

Balance this equation: 2AlBr₃ +

Na₂O --> Al₂O₃ + 6NaBr

Multiple Choice

How many Coppers are in this molecule?

2CuO 

• 4
• 1
• 2
• 3

Multiple Choice

Is this equation balanced?

$$2Cu+O_2\rightarrow2CuO$$  

• Yes

• No

Practice: Balancing Chemical Equations

NaBr Na2 + Br

Draw

Try your best!

Practice: Balancing Chemical Equations

2NaBr Na2 + 2Br

2, 1, 2

Practice :Balancing Chemical Equations
Balance the following chemical equations. Rewrite the equation
in the appropriate format.

1) AlBr₃ + 3 K 3 KBr + Al (1, 3, 3, 1)

2) FeO + PdF₂ FeF₂ + PdO (1, 1, 1, 1) (Balanced)

3) P4 + 6 Br₂ 4 PBr₃(1, 6, 4)

4) 2 LiCl + Br₂ 2 LiBr + Cl₂ (2, 1, 2, 1)

5) PbBr₂ + 2 HCl 2 HBr + PbCl₂(1, 2, 2, 1)

Practice Balancing Equations

next week!