Download Balancing Chemical Equations

Balancing Chemical Equations
What goes in must
come out!
Objectives
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

Learn the steps to balancing chemical
equations.
Take notes to help you understand.
Test yourself with a set of equations to
balance.
Law of Conservation of Mass
You need to remember this law!


The Law of Conservation of Mass states:
that mass is neither created nor
destroyed in any chemical reaction.
Therefore balancing of equations requires
the same number of atoms on both sides of a
chemical reaction.
The number of atoms in the Reactants must
equal the Number of atoms in the Products

To balance an equation you add
COEFFICIENTS. You cannot add or change
SUBSCRIPTS.
Start with a given equation
Mg + O2  MgO
List the atoms that are involved on each side of the
arrow
Mg + O2  MgO
Mg
O
Mg
O
Then start balancing:
[1] Just count up the atoms on each side
Mg + O2 
MgO
1
Mg
1
2
O
1
[2] The numbers aren’t balanced so then add “BIG”
numbers to make up for any shortages
Mg + O2  2 MgO
And adjust totals
1
Mg
1
2
2
O
1
2
But the numbers still aren’t equal, so add
another “BIG” number
2 Mg + O2  2 MgO
2
1
Mg
2
2
O
2
And adjust totals again
NOW BOTH SIDES HAVE EQUAL
NUMBERS OF ATOMS
WE SAY THAT THE
EQUATION IS BALANCED!!
Try to balance these equations using the same
method:
[1] Na + Cl2  NaCl
[2] Al + O2  Al2O3
[3] Li + HNO3  LiNO3 + H2
[4] CH4 + O2  CO2 + H2O
How did you do??
Here are the answers:
[1] 2 Na + Cl2  2 NaCl
[2] CH4 + 2 O2  CO2 + 2 H2O
[3] 2 Li + 2 HNO3  2 LiNO3 + H2
[4] 4 Al + 3 O2  2 Al2O3
Now try these
1) ____ Na3PO4 + ____ KOH  ____ NaOH + ____ K3PO4
2)____ MgF2 + ____ Li2CO3  ____ MgCO3 + ____ LiF
3)____ P4 + ____ O2  ____ P2O3
4)____ RbNO3 + ____ BeF2  ____ Be(NO3)2 + ____ RbF
5)
____ AgNO3 + ____ Cu  ____ Cu(NO3)2 + ____ Ag
6)____ CF4 + ____ Br2  ____ CBr4 + ____ F2
7)__ HCN + __ CuSO4  __ H2SO4 + __ Cu(CN)2
8)____ GaF3 + ____ Cs  ____ CsF + ____ Ga
9)____ BaS + ____ PtF2  ____ BaF2 + ____ PtS
10) ____ N2 + ____ H2  ____ NH3