Download Chemical Equations and Reactions

Chemical Equations and
Reactions
Chapter 8
Modern Chemistry
Do Now
• Each week should be on a new page
• The # of the week should be at the top of
the page
• Each day of the week should be in the
margin
Do Now
Week 18
Monday
Tuesday
Wednesday
Thursday
Friday
Do Now
Complete the following chemical equations.
1. Aluminum + Bromine
AlBr3
2. Sodium + Oxygen
3. Magnesium + Iodine
Na2O
MgI2
Standards
HS-PS1-7: Use mathematical
representations to support
the claim that atoms, and
therefore mass, are
conserved during a chemical
reaction
Essential Question
What are the indications
that a chemical reaction
has taken place?
Vocabulary
Chemical
Reaction
The process by which one ore more
substances are changed into one or
more different substances
Chemical
Equation
Represents, with symbols and formulas,
the identities and relative molecular or
molar amounts of the reactants and
products in a chemical reaction
Precipitate
A solid that is produced as a result of
a chemical reaction in solution and
that separates from the solution.
Chemical Reaction/Equation
Use your periodic table to combine
two elements to create a chemical
reaction. Remember to balance your
charges. Be able to explain your
reaction.
Precipitate
Indications of a Chemical Reaction
Evolution of heat
and light together;
heat or light is not
always a sign of a
chemical change.
What types of common chemical
reactions can you think of that
creates both light and heat?
Indication of a Chemical Reaction
Production of a gas; usually
indicated by the release of
gas bubbles. Example
carbon dioxide being
released when baking soda
is mixed with vinegar
What types of common
chemical reactions can you
think of that creates gas
bubbles?
Indication of a Chemical Reaction
Formation of a
precipitate, if a solid
appears when two
solutions are mixed;
this is evidence of a
chemical reaction.
Silver chromate and Potassium chromate
Color Change
Color change; any change
of color is usually an
indication of a chemical
reaction
What types of common
chemical reactions can
you think of that creates
a color change?
Practice
Write one paragraph to explain the indications of a chemical
reaction. Give an example for each indication.
This is due at the end of the class
Do Now
Write 2-3 sentences to explain the difference
between a chemical reaction and a chemical
equation?
Characteristics of Chemical Equations
A properly written chemical equation
must contain:
1.Known facts – Correct element
symbols, information from a verified
source (periodic table)
2.Correct formulas for the reactants and
products (use charges to create the
correct formulas. Remember the 7
diatomic molecules
3.The law of conservation of mass must
be satisfied – All chemical equations
must be balanced.
Hydrogen
H2
Nitrogen
N2
Oxygen
O2
Fluorine
F2
Clear
Cl2
Brown
Br2
Eyes
I2
Exceptions are S8, and P4
Writing Word and Formula Equations
A word equation is an equation in which the reactants and
products are represented by words.
It has only qualitative meaning, no quantities of reactants or
products are given.
Provide valuable information needed to write and balance a
formula equation.
Example
methane + oxygen →carbon dioxide and water
Writing Word and Formula Equations
A formula equation is an equation in which the reactants and
products are represented by symbols and formulas.
It has only qualitative meaning, until the equation is balanced
are given.
Provide valuable information such as the number of moles or
atoms of the elements or formulas contained in the equation.
Example
methane + oxygen →carbon dioxide and water
CH4(g) + O2(g) → CO2(g) + H2O(g) Unbalanced
CH4(g) + 2O2(g) → CO2(g) + 2H2O(g) balanced
Symbols Used in Chemical Equations
List can be found on page 266 of
your textbook.
Practice
Write word and balanced chemical equations for the following
reaction. Include symbols for physical states when indicated.
Hydrogen peroxide in an aqueous solution decomposes to produces
oxygen and water.
Practice
Write word and balanced chemical equations for the following
reaction. Include symbols for physical states when indicated.
Solid Copper metal reacts with aqueous silver nitrate to produce
solid silver metal and aqueous copper nitrate.
Practice
Write word and balanced chemical equations for the following
reaction. Include symbols for physical states when indicated.
Solid zinc metal reacts with aqueous copper sulfate to produce solid
copper metal and aqueous zinc sulfate
Exit Ticket
Explain why all equations
need to be balanced.
Do Now
Describe a diatomic molecule. List the seven
diatomic molecules that appear on the
periodic table.
What other two element on the periodic table
that cannot exist on their own.
Do Now
Write the word and formula equation for
the chemical reaction that occurs when
solid sodium oxide is added to water at
room temperature and forms sodium
hydroxide(dissolved in water). Try to
balance the equation.
Balancing Chemical Equations
Essential Question
1.What are the step necessary to balance a chemical
equation?
How to Balance an Equation
1. Balance the different types of atoms one at a time
2. First balance the atoms of elements that are combined and that
appear only once on each side of the equation. (start with the largest
compound first)
3. Balance polyatomic ions that appear on both sides of the equation as
single units
4. Balance H atoms and O atoms after atoms of all other elements have
been balanced.
Practice
Write word and balanced equations for the
following. Remember to add symbols for
physical states when indicated.
Use whiteboards.
Practice 1
Nitrogen dioxide gas reacts with
water to form aqueous nitric acid and
nitrogen monoxide gas. (the formula
for nitric acid is HNO3
Practice 2
Solid potassium chlorate
decomposes to form solid
potassium chloride and oxygen
gas.
Practice
Turn to page 274 in your
textbooks, complete practice
problems 1, a,b, and c
Use the steps the you have learned to write the balanced equation for each of
the following:
NaOH Na2O + H2O
Fe + O2 Fe2O3
CO2 + H2O C6H12O6 + O2
FeS + HCl FeCl2 + H2S
O2 + H2 H2O
Cl2 + NaI NaCl + I
Al(NO3)3 + H2SO4 Al2(SO4)3 + HNO3
Check Your Answers
2 NaOH Na2O + H2O
4 Fe + 3O2 2 Fe2O3
6 CO2 + 6 H2O C6H12O6 + 6 O2
FeS + 2 HCl FeCl2 + H2S
O2 + 2 H2 2 H2O
Cl2 + 2 NaI 2 NaCl + I2
2 Al(NO3)3 + 3 H2SO4 Al2(SO4)3 + 6 HNO3
Do Now
Write and balance the formulas from the word equations below.
1. When chlorine gas reacts with methane(CH4), carbon
tetrachloride and hydrogen chloride are produced.
2. When sodium oxide is added to water, sodium hydroxide is
produced.
3. In a blast furnace, iron (III) oxide and carbon monoxide gas
produce carbon dioxide gas and iron.
Do Now
Below is a list of the types of reactions. Read the names
of the reactions and give and explain what is happening
in each type of reaction based on the name.
1.
2.
3.
4.
5.
Composition reactions
Decomposition reactions
Single replacement reactions
Double replacement reactions
Combustion reactions
Types of Reactions
1.
2.
3.
4.
5.
Synthesis reactions
Decomposition reactions
Single displacement reactions
Double displacement reactions
Combustion reactions
You need to be able to identify each type.
1. Synthesis
Example C + O2
C + O O
General:

O C O
A + B  AB
Ex. Synthesis Reaction
Practice
• Predict the products.
2 Na(s) + Cl2(g) 
Mg(s) + F2(g) 
2 Al(s) +3 F2(g) 
2 NaCl(s)
MgF2(s)
2 AlF3(s)
• Now, balance them.
Synthesis Reactions With Oxides
Oxides of active metals react with water to produce
metal hydroxides.
CaO(s) + H2O(l) →Ca(OH)2 (S)
What are some other metals that may react with
water to produce metal hydroxides?
Many oxides of nonmetals react with water to
produce oxyacids.
SO2(g) + H2O(l)→ H2SO3
Do Now
Describe a composition (synthesis)
reaction. Use you period table to create
three examples.
Essential Question
How is a decomposition reaction different
from a synthesis reaction?
2. Decomposition
Example: NaCl
Cl Na

General:
Cl
+
Na
AB  A + B
Decomposition Reaction
There are many types of decomposition
reactions. Decomposition reactions are the
opposite of synthesis reactions.
Five types of decomposition reactions are:1. Decomposition of binary compounds
2. decomposition of Metal Carbonates
3. Decomposition of Metal Hydroxides
4. Decomposition of Metal chlorates
5. Decomposition of Acids
Ex. Decomposition Reaction
Decomposition of Binary Compounds
• Simplest kind of decomposition
reaction
• Decomposed with heat or electricity
(electrolysis)
• Less active metal oxides decompose
with heat
• Decomposes into its elements
Practice
Remember: Compound will be decomposed into
its elements
HgO --->
H2O --->
MgCl2 --->
FeS --->
Decomposition of Metal Carbonates
• Decomposes to produce a metal oxide and carbon
dioxide gas.
Practice
CaCO3 --->
Na2CO3 --->
Decomposition of Metal Hydroxides
• All except for group 1 metals
• Decompose when heated to yield metal oxides
and water.
Practice
Ca(OH)2 --->
NaOH --->
Decomposition of Metal Chlorates
• When heated, metal chlorates decompose to
form a metal chloride and oxygen.
Practice
KClO3 --->
Ba(ClO3)2 --->
Decomposition of Acids
Some acids decompose into nonmetal oxides
and water.
Practice
H2CO3 →
H2SO4→
More Practice
1.ZnCO3 →__________
6. H2CO3 →__________
2. Ba(ClO3)2 →_______
7. Ba(OH)2 →________
3. Sb2O5→___________
8. HgO →___________
4. CaCO3→__________
9. NaCl →___________
5. KClO3→___________
10. H2SO4→_________
Exit ticket
Describe a decomposition
reaction
3. Single Displacement
Example: Zn + CuCl2
Cu
Cl
+
Cl
General:
Zn

Zn
Cl
+
Cu
Cl
AB + C  AC + B
Single Displacement
• Also known as
replacement
reactions
• One element
replaces a similar
element in a
compound
• Commonly
occurring in
aqueous solutions
Practice
l. Ag
2. Zn
+
+
KNO3
AgNO3
----->
----->
Practice
3. Al
4. Cl2
5. Li
+
H2SO4
+ KI
+
----->
----->
H2O ----->
More Practice
5. Li
6. Cu
+
H2O ----->
+
FeSO4 ----->
7. Na +
H2O ----->
8. Fe
+
Pb(NO3)2
9. Cu
+ H2O ----->
10. Cu
+
Al2(SO4)3
----->
----->
Single Displacement/Rule Exceptions
• Displacement of hydrogen in water by a metal
• Produces metal hydroxides and hydrogen
Ex.
Na(s) + H2O(l) →
2 Na(s) + 2 H2O(l) → 2 NaOH(aq) + H2(g)
Single Displacement/ Rule Exceptions
• Displacement of Halogens
• Displacement depends on the position of the
halogen in the group
• Each element can replace any element below it, but
not any element above it.
Cl2(g) + 2KBr(aq) → 2KCl(aq) + Br2(l)
Br2(l) + KCl(aq) → no reaction
Exit Ticket
In a single replacement reaction, one
___________________ replaces a
_______________ element in a
compound.
Cl2
+
NaI-----→
Ex. Single Replacement Reaction
Single Replacement Reactions
• Write and balance the following single replacement reaction
equation:
• Zn(s) + HCl(aq)  2 ZnCl2 + H2(g)
• 2 NaCl(s) + F2(g) 2 NaF(s) + Cl2(g)
•2 Al(s)+ 3 Cu(NO3)2(aq) 3 Cu(s)+ 2 Al(NO3)3(aq)
4. Double displacement
Example: MgO + CaS
Mg
+
O
General:
Ca
S

Mg
S
+
Ca
O
AB + CD  AD + CB
Double Displacement
• Ions of two compounds exchange places in an
aqueous solution to form two new compounds.
• Compounds formed are usually precipitates, gas or
molecular compounds
Double Replacement Reactions
• Think about it like “foil”ing in algebra, first and last ions go
together + inside ions go together
• Example:
AgNO3(aq) + NaCl(s)  AgCl(s) + NaNO3(aq)
• Another example:
K2SO4(aq) + Ba(NO3)2(aq)  KNO3(aq) + BaSO4(s)
2
Practice
•
1.
2.
3.
4.
5.
6.
Predict the products.
HCl(aq) + AgNO3(aq) 
CaCl2(aq) + Na3PO4(aq) 
Pb(NO3)2(aq) + BaCl2(aq) 
FeCl3(aq) + NaOH(aq) 
H2SO4(aq) + NaOH(aq) 
KOH(aq) + CuSO4(aq) 
5. Combustion Reactions
• Combustion reactions - a
hydrocarbon reacts with
oxygen gas to release large
amounts of energy in the
form of heat and light
• This is also called burning!!!
Combustion Reactions
• In general:
CxHy + O2  CO2 + H2O
• Products are ALWAYS
carbon dioxide and water.
(although incomplete burning does
cause some by-products like carbon
monoxide)
• Combustion is used to heat homes
and run automobiles (octane, as in
gasoline, is C8H18)
Combustion
• Example
6
5
• Write the products and balance the following combustion reaction:
•
C5H12 + O2  CO2 +8H2O
• C10H22 + O2 
Practice
1.
2.
3.
4.
5.
6.
7.
8.
methane (CH4) +
ethane (C2H6) +
propane (C3H8) +
butane (C4H10) +
pentane (C5H12) +
hexane (C6H14) +
ethene (C2H4) +
ethyne (C2H2) +
oxygen
oxygen
oxygen
oxygen
oxygen
oxygen
oxygen
oxygen
Mixed Practice
•
State the type & predict the products.
1.
2.
3.
4.
5.
BaCl2 + H2SO4 
C6H12 + O2 
Zn + CuSO4 
Cs + Br2 
FeCO3 
Exit Ticket
List and describe the five
types of chemical
reactions.