UNIT 6: CHEMICAL EQUATIONS (chapter 8)
Section 1: What is a Chemical Reaction?

Chemical Reaction: ___________________________________________________________________________
___________________________________________________________________________________________
___________________________________________________________________________________________
o REACTANTS
(YIELDS)
____________________________
____________________________
Set of atoms in a particular
arrangement

PRODUCTS
___________________________
___________________________
same set of atoms in a different
arrangement
Evidence of a chemical reaction:
o _______________________________________
o _______________________________________
o _______________________________________
o _______________________________________
o _______________________________________
Section 2: How are Chemical Equations for Reactions Written?

Word Equations: written in words not symbols/formulas
o Hydrogen reacts with chlorine to produce hydrogen chloride
o Word form: ______________________ + ______________________  __________________________

Formula Equations: written using formulas/symbols of elements/compounds
o Hydrogen reacts with chlorine to produce hydrogen chloride
o Formula Form: __________________ + __________________  ______________________

Diatomic Elements: containing 2 atoms—these are elements that do not exist singularly in nature because they
are highly reactive
o HINT: Which elements are diatomics? “HON, it’s the halogens!”

o
Diatomic Elements: N, O, F, Cl, Br, I, H
o
This means that when these elements are found by themselves in an equation, they are typically
diatomic, meaning they have a subscript of “2”; i.e. N2, H2, F2, I2, Br2, Cl2, O2: MEMORIZE THESE!!!!!
Balancing Equations
o Chemical formula equations MUST be __________________________; to demonstrate there is an
_____________________________________________________________________________________
_____________________________________________________________________________________
 This is due to ___________________________________________________________________
o
When you balance equations  USE ________________________________________________!!!!!
o Never, EVER by changing subscripts!!!!! This is important!!!!!
o
______H2 + Cl2  ______HCl (unbalanced—this is what you would see—base equation)
o
______H2 + Cl2  ___2___HCl (balanced—this is what you need to do)
o
How to do this—count how many of each _______________ is on product side and on reactant side;
make sure they are _____________________!!!

Example 1:____H2 + ____Cl2 → ____HCl
o Before Balancing:
o
Reactants
Products
Hydrogen
2
Hydrogen
1
Chlorine
2
Chlorine
1
This shows you that you need more hydrogen & chlorine in the products—decide how to get them equal
on both sides
In this case, add a coefficient “2” to HCl, then redo your counts—now 2 of H & Cl on both sides
o
Balanced Equation:____H2 + ____Cl2 → ____HCl
o
Coefficient applies to ALL elements in that compound
o

Example 2: ___Mg + ___O2 → ___MgO
o Before Balancing:
Reactants
Products
Magnesium
Magnesium
Oxygen
Oxygen
o
o
After Balancing:
___________Mg + __________O2 → __________MgO
Reactants
Magnesium
Oxygen

Products
Magnesium
Oxygen
Practice Problems: Balance the following:
a. ________N2 + _________H2  _________NH3
b. ________H2O2  _________H2O + __________O2
c. ________Na + ________O2 → ________Na2O
d. ________Cu2O + ________C → ________Cu + _________CO2
e. ________Mg + ________HCl → ________MgCl2 + _________H2
f.
________KI + ________Pb(NO3)2  ____________PbI2 + _____________KNO3
Section 3: Types of Chemical Reactions and How to Predict Products of Reactions

5 types of chemical reactions—Review—See explanations of each on other notes page.
1. ___________________________________
 Multiple reactants form a single product

______________________ + ____________________  _______________________

A + B  AB

When predicting products, ________________________________________________________
______________________________________________________________________________
2. ___________________________________
 Single reactant breaks down into multiple products

_______________________  __________________________ + _______________________

AB  A + B

See Decomposition Handout for how to predict products
3. ___________________________________

One free element replaces an element in the compound

_________________ + _________________  _________________ + __________________

A + BC  AC + B

When predicting products, ________________________________________________________
(or A + BC  BA + C)
______________________________________________________________________________
4. ___________________________________
 Exchange of ions between compounds

_________________ + _________________  _________________ + __________________

AB + CD  AC + BD

When predicting products, ________________________________________________________
(or AB + CD  AD + BC)
______________________________________________________________________________
______________________________________________________________________________
5. ___________________________________
 _________________ + _________________  _________________ + __________________

CxHy + O2  CO2 + H2O

When predicting products, ________________________________________________________
______________________________________________________________________________


Classification Practice Problems: Classify the types of reactions they are.
1. CuO + H2  Cu + H2O
_____________________________________
2. 2H2O2  2H20 + O2
_____________________________________
3. 2Ag + S  Ag2S
_____________________________________
4. C4H8 +6O2  4CO2 + 4H2O
_____________________________________
5. 2K + 2H2O  2KOH + H2
_____________________________________
6. HCl + NaOH  H2O + NaCl
_____________________________________
Practice Problems: For the reactions below predict the products that would be formed.
1. ZnSO4 + Cu(NO3)2 

Equation Type:____________________________
2. Mg + Pb(NO3)2 

Equation Type:_____________________________
3. Al2(CO3)3 

Equation Type:______________________________
4. C2H8 + O2 

Equation Type:________________________________
5. Mg + P 


Equation Type:_________________________________
Practice Problems: Predict the products formed in each of the following reactions and write a balanced equation.
1. the decomposition of barium hydroxide
2. the reaction of mercury (II) and oxygen
3. the reaction of sulfuric acid and potassium hydroxide
4.
the combustion of cyclopentane, C5H10
5. The reaction of magnesium and potassium chloride
Section 4: What Does a Chemical Equation Tell You?

Reaction Conditions & Physical State
o “Symbols Used in Chemical Equations”
Symbol

+
Δ
NR
(s)
(l)
(g)
(aq)

Measuring Stuff: What is a Mole?
o Mole (mol): amount of a substance that contains ____________________________________________
____________________________________________________________________________________
o
o

Meaning
Avogadro’s Number:
6.022 x 1023: _________________________________________________
_____________________________________________________________________________________
Example:
 1 mole O2 = __________________________ atoms O2
 1 mole HCl = __________________________atoms HCl
Quantitative Relationships
o Mole Ratios: _________________________________________________________________________
o In the reaction: 2 H2 + O2  2H2O; the mole ratio is
_______________________ : _________________________ : _________________________
o
In the reaction: C6H12O6 + 6 O2  6 CO2 + 6 H2O, the mole ratio is:
_____________________ : ___________________ : _____________________ : ___________________
o
MOLE RATIO Practice:
 Example: C6H12O6 + 6 O2  6 CO2 + 6 H2O
 How many moles of CO2 can be produced from 3 moles of C6H12O6?


Example: C6H12O6 + 6 O2  6 CO2 + 6 H2O
Calculate the number of moles of H2O produced by 0.42 mol C6H12O6 during cellular respiration.