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Transcript of Take out your Homework. Identify the reactants and products in the following chemical reaction...
Balancing Chemical Equations and Types of Chemical Reactions
09.24 & 09.25 2012Boon Chemistry
Catalyst Take out your Homework. Identify the reactants and products in
the following chemical reaction equations:› 2 Mg (s) + O2 (g) 2 MgO (s)
› CH4 (g) + 2 O2 (g) CO2 (g) + 2 H2O (l)
Write the chemical reaction equation for the following description:› Hydrogen gas and oxygen gas combine to form
liquid water.
Catalyst Answers: Take out your Homework. Identify the reactants and products in the
following chemical reaction equations:› 2 Mg (s) + O2 (g) 2 MgO (s)
› CH4 (g) + 2 O2 (g) CO2 (g) + 2 H2O (l)
› Reactants are on the left and products on the right of the arrow.
Write the chemical reaction equation for the following description:› Hydrogen gas and oxygen gas combine to form liquid
water.
› 2 H2 (g) + O2 (g) 2 H2O (l)
Objectives I can compare and contrast different
types of chemical reactions.
I can define and identify a balanced chemical equation.
I can balance simple chemical equations.
Agenda Catalyst (10) Balancing Notes & HW Review (20) Group Work: Balancing Chemical
Equations. (40) Types of Chemical Equations Reading
Activity (40)› Group Work (20)› Presentations & Debrief (20)
Exit Slip (10)
Why do we balance Chemical Reactions?
Law of Conservation of Mass
Matter cannot be created or destroyed in a chemical reaction
The number of atoms on the reactant side must equal the atoms of the products
+H2 H2OO2(g) (g) (l)
H H O O HH O
Unbalanced!
HH OH H
Balanced!
Balanced Chemical Equations A chemical equation is “balanced” when
there are the same number of atoms of each element on both sides of the arrow.
NaHCO3 (s) + HC2H3O2 (aq) èNaC2H3O2 (aq) + CO2 (g) + H2O (l)
Is it balanced?Reactants ProductsNa = 1 Na = 1
H = 5 H = 5
C = 3 C = 3
O = 5 O = 5
Is it balanced? Practice Determine the number of atoms of
each element in the reactants and products. Then, state whether the equation is balanced.
1. P4 + O2 → P2O5
2. C3H8 + O2 → CO2 + H2O
3. Ca2Si + Cl2 → CaCl2 + SiCl44. Si + CO2 → SiC + SiO2
Not balanced.Not balanced.
Not balanced.
Not balanced.
Balancing Equations
Only the coefficients can be changed!
H2 H2O+ O2(g) (g) (l)
H =
O =
H =
O =
2
2
2
1
coefficient
2
4
2
2
4
Balancing Tips
Always balance non-Oxygen’s & Hydrogen’s first (ex. Chlorine)
Then balance Hydrogens Balance Oxygens Last
Balancing Practice!1. P4 + O2 → P2O5
P4 + 5 O2 → 2 P2O5
2. C3H8 + O2 → CO2 + H2O
C3H8 + 5 O2 → 3 CO2 + 4 H2O
3. Ca2Si + Cl2 → CaCl2 + SiCl4Ca2Si + 4 Cl2 → 2 CaCl2 + SiCl4
4. Si + CO2 → SiC + SiO2
2 Si + CO2 → SiC + SiO2
Group Work: Balancing Equations
Instructions: › Work with the person next to you. › You have two worksheets to work on.
1. “Is it balanced?” Determine whether the chemical equation is balanced by counting atoms in the reactants and products.
2. “Balancing Act” Practice balancing equations.› What you do not finish is homework.› Ms. Boon will stamp your work when you are
done.› Once you have a stamp, you may check your
answers on the posted answer sheet.
Balancing Act Notes Atoms are not created or destroyed
during a chemical reaction. Scientists know that there must be the
same number of atoms on each side of the equation.
To balance the chemical equation, you must add coefficients to the different parts of the equation.
Chemical Reactions Reading You will work in groups of four or five at your table. Fold a sheet of paper into four squares. Label each square:
1. Synthesis reaction2. Decomposition reaction3. Single Replacement Reaction4. Double Replacement Reaction
You will be assigned one reaction. Read the section on that reaction, define it, give
an example, and draw a picture in your chart. (7 min)
Take turns sharing with your group. (8 min) Take notes on the other 3 reactions. If you finish early, read the entire article.
1. Synthesis Reactions Two substances combine to make one Synthesis means “to make”
+H2 H2OO2(g) (g) (l)
H H O O
H H H HO
H
H O
A + B AB
SYNTHESIS
Na + Cl2 NaCl
2. Decomposition Reactions One substance breaks down into 2 Decomposition means “to break down”
or “decay”
H HN
+NH3 H2(g)(l) N2 (g)
H
H HNH
AB A + B
Decomposition
NaCl Na + Cl2
one element replaces another in a compound
3. SINGLE REPLACEMENT
AB + C AC + B
Single Replacement Reaction
AB + C AC + B or CB + A
Single Replacement
NaBr + Cl2 NaCl + Br2
4. DOUBLE REPLACEMENT
Both elements in two compounds switch
places AB + CD AD +
CB
Double Replacement
NaBr + Pb2S3 Na2S + PbBr3
K2SO4 + Ba(OH)2
KOH + BaSO4
5. Combustion Reactions A hydrocarbon reacts with oxygen gas to
produce carbon dioxide and water vapor Combustion means to “burn in oxygen”
+CH4 H2OO2 CO2 +
+C2H4 H2OO2 CO2 +
+C6H12O6 H2OO2 CO2 +
Exit Slip! Balance and Identify the Type of Reaction.
1. Mg + O2 MgO
2. C3H8 + O2 CO2 + H2O
3. Na + Cl2 NaCl
4. C6H6 C + H2
5. FeO + CO2 FeCO3
Homework
Read pp. 271-274 Do problems pp. 271 #1-3, pp. 298 #1,
2, 3, 5, 6, 7