Download Writing and Classifying Balanced Equations

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Date:___________
Block:_____
Writing and Classifying Balanced Equations
Part 1. Balancing Chemical Equations – Using CH4 as a model.
To understand balancing we are going to make reactant molecules and take them apart to make product molecules.
This way you will see exactly how the atoms are rearranged.
1.
Use your molecular models to make the following reactants: methane (CH4) and oxygen (O2). Make a colored
sketch of both be sure to use VSEPR shaping. Label your atoms.
2.
Now we are ready to form products. Below is the equation for the combustion of methane:
CH4 + O2 → CO2 + H2O
3.
a.
b.
_______________
________________
Label the reactant and the product side of the equation.
What is carbon bonded to on the products side?
c.
What must happen to CH4 for this to occur?
Try to make both of the product molecules: water and carbon dioxide, from your CH4 and O2
molecules, by breaking them apart and reconnecting the atoms. Remember the Law of Conservation of Mass states
that you cannot just add atoms.
a.
What happens? Explain what you are able to make.
b.
What additional atom(s) do you need to complete both the water and carbon dioxide molecules?
c.
After you make the molecules are there any atoms left over?
Now balance the equation.
_____CH4 + ____O2 → _____CO2 + _____H2O
Work with your partner and follow the above equation. Model this chemical equation. Do you have any leftovers now?
Sketch out your new equation.
4.
Are there any left over atoms this time?
5.
Do you think that mass was conserved? Explain briefly.
Name: ______________________________
Date:___________
Block:_____
Homework Day _____________. This is due on ________________.
Read pp. 298 & 299 from NAC before completing the following questions. Answer the following questions:
1. What is the Law of Conservation of Mass?
2. How does the Law of Conservation of Mass relate to balancing chemical equations?
3. What is an unbalanced chemical equation? How does it break the Law of Conservation of Mass?
4. Use the words subscript and coefficient to explain how to balance chemical equations.
5. What number do you never write as a coefficient?
Remember your rules for Interpreting Chemical Formulas
2 Na3PO4
NaC2H3O2
Ca(NO3)2
4 Ca(NO3)3
Write the word or words that best completes each sentence.
balanced, product, separation, reactants, chemical reaction, or element
1.
When reading a chemical equation a plus sign (+) indicates a/an
substances that are mixed together or produced.
2.
Consider the equation: sulfur + oxygen → sulfur dioxide.
a.
The elements on the left side of the arrow are called the
b.
The compound on the right side of the arrow is called a/an
during the chemical reaction.
3.
If a chemical reaction is properly
same on both sides of the arrow.
4.
Chemical equations are a simple way to describe the overall process of a/an
between different
.
, because it is created
the number of atoms of each type of element will be the
_.
Name: ______________________________
Date:___________
Block:_____
Place the letter of the correct word or phrase from the list on the right next to
each statement.
5.
6.
7.
The total mass of the reactants and products must
be the same on both sides of the arrow.
This is what in the chemical equation: S + O2→ SO2
the ingredients S and O2 are called.
In the compound P2O5 the numbers 2 and 5 tell
us how many of each type of atom are in the molecule.
8.
This is the name for the chemical substance(s) formed during a
chemical change.
9.
When balancing a chemical equation we can add these numbers
in front of a substance, such as the 2 in front of ammonia shown here: 2N
a)
subscript
b.
product
c.
law of conservation of
mass
d.
coefficient e.
reactant
f.
arrow
Consider the following chemical equation: Na(s) + 2H2O(l) → 2NaOH + H2
10. How many H atoms are on the reactants side of the equation?
11. How many H atoms are on the products side of the equation?
12. Is the number of O atoms the same on both sides of the arrow?
13. Is the equation completely balanced as written?
14. If no, what would need to be done to make it balanced. Explain with a sentence and write the final balanced
equation.
Name_________________________________________
Date___________
Block____
Part 2. Five Types of Chemical Reactions
Instructions: Carefully study these five types of chemical reactions and answer the questions.
**A, B, and C represent pure substances. AB, CD, AC, BC, AD, and CB are all compounds.
**CxHyOz represents a fuel or any compound made up of carbon, hydrogen, and/or oxygen
Notes:
a. Combination:
A + B

AB
b. Decomposition:
AB

A + B
c. Single Replacement
AB
+ C

AC + B
AB
+ C

BC
+ A
d. Double Replacement:
AB
+ CD
AD
+ CB
e. Combustion:
CxHyOz

+ O2 
CO2 + H2O
1. Examine the patterns in each of the 5 reactions above and the vocabulary in the introduction. Write a sentence to describe
each of the 5 reaction types. The first one has been completed as an example.
a. combination:
two pure substances combine to make a compound.
b. _____________________________________________________________________________
c. _____________________________________________________________________________
_____________________________________________________________________________
d. _____________________________________________________________________________
_____________________________________________________________________________
e. _____________________________________________________________________________
2. Which reaction type do you think is the most specialized or specific? Support your answer.
_____________________________________________________________________________
_____________________________________________________________________________
Name_________________________________________
Date___________
Block____
Writing balanced equations
Instructions: Examine the following diagrams of molecules performing chemical changes. For each of the examples
a. Write the skeleton equation to show each substance as it occurs in the diagrams. Compounds are shown with
their atoms touching each other and have a subscript in their chemical formula representing the number of
atoms bonded together. For example is NH3
b. Balance the equation using coefficients. A coefficient tells the number of molecules needed to make the number
of atoms of each element equal on both sides of the equation.
c. Classify the equation as one of the 5 types from the introduction.
Example 1: Nitrogen
+
N
N
N

Hydrogen
Ammonia or NH3
H
+
H
N
H
H
H
Example 2:
Methane gas
H
H
H
C
+
oxygen
+
O
O
H
Example 3: Hydrogen and chlorine form hydrogen chloride
+

carbon dioxide +
water
+
O
C
O
H
H
O
Name_________________________________________
Date___________
Block____
Example 4: Hydrogen and oxygen form water.
Example 5: Calcium and water form calcium hydroxide and hydrogen
H
C
a
H
O
O
Ca
H
H
H
O
H
Example 6: Calcium chloride and sodium hydroxide form calcium hydroxide and sodium chloride.
Cl
N
a
Ca
O
O
H
Na
H
Ca
Cl
Cl
H
O
Example 7: Ethylene gas
H
H
C
H
oxygen 
+
C+
carbon dioxide +
O
O
H
water
H
O
C
O
H
O
Name_________________________________________
Date___________
Block____
Example 8: Propane + oxygen  carbon dioxide and water

Example 9:

Sodium and chlorine combine to form sodium chloride.

N
a
Cl
N
a
Cl
Cl
Balance the following equations using coefficients. Subscripts have been completed for you. In the blank to the far right, state
the type of reaction.
1.
___ Al +
___ O2

___ Al2O3
2.
___CH4 +
___O2

___ CO2
+
___ H2O
_________________
3.
___HgO

___Hg
+
___O2
_________________
4.
___Pb(NO3)2
+

___PbCrO4
+
___KNO3
_________________
5.
___Fe
+

___FeCl2
+
___Cu
_________________
___K2CrO4
___CuCl2
_________________
Name_________________________________________
Date___________
Block____
Homework Day _____________. This is due on ________________.
Balance the following equations using coefficients. Subscripts have been completed for you. In the blank to the far right, state
the type of reaction.
1.
___Fe
+
___O2

___Fe2O3
2.
___Mg
+
___HCl

___H2
+
___MgCl2
_________________
3.
___Al(OH)3
+
___HCl

___AlCl3
+
___H(OH)
_________________
4.
___ H2
+
___N2

___NH3
5.
___KClO3

___KCl
+
___O2
_________________
6.
___Fe

___FeCl2
+
___Cu
_________________
7.
___H2O2

___H2O
+
___O2
_________________
8.
___Fe
+
___Cl2

___FeCl3
9.
___NaOH
+
H2SO4

___Na2SO4
+
10.
___Al(NO3)3
+
___FeCl2

___Fe(NO3)2
+ ___AlCl3
_________________
11.
___CH4O
+
___O2

___CO2
+
_________________
12.
___C3H5(NO3)3
+
___CuCl2
 ___CO2 + ___N2
_________________
_________________
_________________
___H(OH)
___H2O
+ ___H2O + ___O2
Write a step-by-step process for writing, balancing, and classifying a chemical equation.
_________________
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