Balancing Chemical Reactions
Thursday, November 20 & Monday,
December 1
Do Now
• What are the general equations for the 4
types of chemical reactions we learned
about earlier this week?
Types of Chemical Reactions
• What are the general equations for the 4
types of chemical reactions we learned
about earlier this week?
1.
2.
3.
4.
Synthesis: A + B  AB
Decomposition: AB  A + B
Single Replacement: AB + C  CB + A
Double Replacement: AB + CD  AD + CB
Types of Reactions: SYNTHESIS
A
+
B

C
Types of Reactions: DECOMPOSITION
AB
 A +
B
Types of Reactions:
SINGLE REPLACEMENT
A + BC  AC + B
Types of Reactions:
DOUBLE REPLACEMENT
AB + CD
 DA
+
BC
Objective
• I can balance chemical equations using
coefficients according to the Law of
Conservation of Mass
HONORS
Chemical Reactions Lab Recap
• Due Friday 11/25
• 3 types of reactions: synthesis, single
replacement, and double replacement
• Observations complete for the following
reactions
1. Iron and sulfur
2. Copper and silver nitrate
3. Calcium chloride and sodium carbonate
4. Sodium bicarbonate and acetic acid
Homework
• Due Monday/Tuesday, December 1/2:
balancing chemical equations Homework
• Turn in: types of chemical reactions
vocabulary foldable
Agenda
1.
2.
3.
4.
5.
6.
7.
Do Now, Objective (8 min)
Law of Conservation of Mass Intro (8 min)
Balancing Reactions Notes (6 min)
Balancing Rxns Guided Practice (10 min)
Balancing Rxns Game (10 min)
Balancing Rxns Onion (15 min)
Balancing Rxns Independent Practice (10
min)
Law of Conservation of Mass Intro
• Watch the video on the Law of
Conservation of Mass. Then, write 1-2
sentences explaining why this is an
important idea in our unit on chemical
reactions.
http://www.brainpop.com/science/matteran
dchemistry/conservationofmass/
Think Pair Share
• What does the law of conservation of mass
say?
• ¿Qué dice la ley de conservación de la masa?
Foldable Notes: Subscripts
N2 + 3 H2  2NH3
• Subscript: how many atoms of an
element are in a molecule or
compound
• Subíndice: cuántos átomos de un
elemento en una molécula o compuesto
*subscripts can’t change!
Foldable Notes: Coefficient
Rb + S4  2RbS2
• Coefficient: represent the number of
molecules or formula units that are
involved in a reaction
• Coeficiente: cuántas moléculas están
involucradas en una reacción
*coefficient can change!
Thumbs Up, Thumbs Down
N2 + 3H2  2NH3
Rb + S4  2RbS2
1. Is the first equation balanced? How do you
know?
- Yes. There are the same number of atoms of each element
in the reactants and the products. 2 nitrogen atoms, and 6
hydrogen atoms
2. Is the second equation balanced?
- No. There is 1 Rb atom in the reactants, and 2 in the
products. It does not follow the law of conservation of mass
Balancing Reactions: Guided Practice
• You’ve just cashed your paycheck and you’re
ready for a night out with your friends. You’ve
got money- Why not splurge a little? The next
morning you check your pockets to figure out
how much you spent. WHOA! Where did your
paycheck go?!? So you hunt a little find your
receipts to piece together where your money
has gone…
Balancing Reactions: Guided Practice
• You started with $150
– Below is a list of your expenses
• $35 – dinner
• $24.50 – movie tickets
• $45 – shopping spree
1. How much money are you trying to
account for?
2. How much is not accounted for?
Balancing Reactions: Guided Practice
• You started with $150
– Below is a list of your expenses
• $35 – dinner
• $24.50 – movie tickets
• $45 – shopping spree
1. How much money are you trying to
account for? $150 total
2. How much is not accounted for? $45.50
A Balancing Act
• In chemical equations all of our atoms must
be accounted for.
• We call this the law of conservation of mass,
in which no mass is created or destroyed.
• A esto le llamamos la ley de conservación de
la masa, en el que se crea ninguna masa o
destruidos.
• To make sure our work holds true, we balance
chemical equations.
Balancing Chemical Equations – Example 1
C5H10O + 7O2  5CO2 + 5H2O
Element
Reactants
Products
Carbon (C)
5
5
Hydrogen (H)
10
5*2 = 10
Oxygen (O)
14+1 = 15
5*2 +5*1 = 10+5 = 15
*When you have a coefficient in a chemical equation.
Multiply the coefficient by the subscript to get the
number of atoms of that element in the reaction.
Balancing Reactions: Example 2
SnO2 + H2  Sn + H2O
Element
Tin (Sn)
Oxygen (O)
Hydrogen (H)
Reactants
Products
 This reaction is unbalanced. You need to change the
COEFFICENTS to balance it and obey the law of conservation
of mass!
Balancing Reactions: Example 2
1SnO2 + 2H2  1Sn + 2H2O
SnO2 + 2H2  Sn + 2H2O
Guided Practice
• Balance the reaction below using a ‘balancing
table’
__Fe2O3 (s) + ___CO (g)  ___Fe(l) + ___ CO2(g)
Element
Fe (iron)
O (oxygen)
C (carbon)
# Atoms in
Reactants
# Atoms in
Products
Guided Practice
___H3PO4 + ____HCl  ____PCl5 + ___H2O
Element
H (hydrogen)
P (phosphorous)
O (oxygen)
Cl (chlorine)
# Atoms in
Reactants
# Atoms in
Products
Guided Practice
___Na3PO4 + ___HCl  ___ NaCl + ___H3PO4
Element
Na (sodium)
P (phosphorous)
O (oxygen)
H (hydrogen)
Cl (chlorine)
# Atoms in
Reactants
# Atoms in
Products
Balancing Reactions Game – 10 minutes
• Go to Ms. Bergman’s website and play the
‘balancing reactions’ game for more practice
balancing chemical equations
1. Write down the balanced chemical equations in
your notes
http://sbergman.weebly.com/chemistry-unit-3--chemical-reactions.html
Balancing Reactions Recap
• Chemical Reactions must have equal numbers
of each type of atom on both sides of the
reaction arrow
• Reacciones químicas deben tener el mismo
número de cada tipo de átomo en ambos
lados de la flecha de reacción
__Fe2O3 + __CO  __Fe + __CO2
Fe2O3 + 3CO  2Fe + 3CO2
Balancing Reactions Onion Practice
• Balance 5 chemical equations using your
“onion”
– The inside layer is the most difficult!
– Write down all 5 balanced reactions in your notes
– Use a balancing table to help as needed
Element Reactants Products
Onion Answers!
1.
2.
3.
4.
5.
6.
7.
2Fe + 3Cl2  2FeCl3
4Fe + 3O2  2Fe2O3
BaCl2 + Na2SO4 + H2O  BaSO4 + 2NaCl
Ca + 2H3N  Ca(NH2)2 + H2
C4H6O3 + H2O  2C2H4O2
10HSiCl3 + 15H2O  H10Si10O15 + 30HCl
6XeF4 + 12H2O  2XeO3 + 4Xe + 24HF + 3O2
Balancing Equations Practice
• If you finish early work on your balancing
reactions homework problems (#1-20)
Balancing Equations Day 2
• Do Now, Objective (10 min)
• Review steps of balancing equations (10 min)
• Balancing equations whiteboard practice (10
min)
• Balancing Equations Group Practice (15 min)
• Independent practice balancing (20 min)
• Balancing equations quiz (10 min)
Do Now
Balance the chemical equation below:
H2 + O2  H2O
Do Now
Balance the chemical equation below:
2H2 + O2  2H2O
Objective
• I can balance chemical equations
using coefficients according to the
Law of Conservation of Mass on a
balancing reactions quiz
Homework
Turn in: balancing chemical
equations homework from before
Thanksgiving Break
Agenda
1.
2.
3.
4.
5.
6.
Do Now, Objective (8 min)
Review Balancing Reactions (10 min)
Balancing Reactions Whiteboard Practice (10 min)
Balancing Reactions with Partners (15 min)
Balancing Reactions Independent Practice (20 min)
Balancing Reactions Quiz (10 min)
A Balancing Act
• In chemical equations all of our atoms must
be accounted for.
• We call this the law of conservation of mass,
in which no mass is created or destroyed.
• A esto le llamamos la ley de conservación de
la masa, en el que se crea ninguna masa o
destruidos.
• To make sure our work holds true, we balance
chemical equations.
Balancing Chemical Equations – Example 1
C5H10O + 7O2  5CO2 + 5H2O
Element
Reactants
Products
Carbon (C)
5
5
Hydrogen (H)
10
5*2 = 10
Oxygen (O)
14+1 = 15
5*2 +5*1 = 10+5 = 15
*When you have a coefficient in a chemical equation.
Multiply the coefficient by the subscript to get the
number of atoms of that element in the reaction.
Balancing Reactions: Example 2
SnO2 + H2  Sn + H2O
Element
Tin (Sn)
Oxygen (O)
Hydrogen (H)
Reactants
Products
 This reaction is unbalanced. You need to change the
COEFFICENTS to balance it and obey the law of conservation
of mass!
Balancing Reactions: Example 2
1SnO2 + 2H2  1Sn + 2H2O
SnO2 + 2H2  Sn + 2H2O
WHITEBOARD PRACTICE
Balance the chemical reaction below:
N2 + H2  NH3
WHITEBOARD PRACTICE
Balance the chemical reaction below:
KClO3  KCl + O2
WHITEBOARD PRACTICE
Balance the chemical reaction below:
NaCl + F2  NaF + Cl2
WHITEBOARD PRACTICE
Balance the chemical reaction below:
AlBr3 + K2SO4  KBr + Al2(SO4)3
WHITEBOARD PRACTICE
Balance the chemical reaction below:
CO2 + H2O  C6H12O6 + O2
WHITEBOARD PRACTICE
Balance the chemical reaction below:
K + MgBr  KBr + Mg
WHITEBOARD PRACTICE
Balance the chemical reaction below:
HCl + CaCO3  CaCl2 + H2O + CO2
WHITEBOARD PRACTICE
Balance the chemical reaction below:
H2SO4 + NaNO2  HNO2 + Na2SO4
Balancing Reactions Group Practice
• Working in groups of 2-3, use the reaction
cards to balance reactions 1-12 on your
activity sheet.
• This activity is graded for accuracy.
– 12 points for types of reaction
– 12 points for correctly balancing the equation
Independent Practice
• Practice balancing chemical equations using
either your Balancing Reactions Homework
OR Chemical Equations & Reaction Types,
Quiz
• Complete your quiz silently. When you are
finished, turn it in, and wait quietly until the
end of class.