1. Balancing Chemical Reactions
Chemistry
Balancing Chemical Reactions

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3. Balanced Chemical Equations……
A balanced equation has the same number of each element _________

4. Chemical Reactions
While the reactions show what is used up and what is produced, they do not reflect the proper number of each type of atom required for the reaction.
H O2  H2O
How many oxygen atoms are on the right?
_________
How many oxygen atoms are on the left?
Does this make sense? What happened to that other oxygen atom.
We use coefficients to “balance the equation” ensure that there are the same number of each type of atom on either side of the equation.
Afterwards check to make sure the number of atoms on the left = the right
**Using coefficients doesn’t change the reaction, it simple shows us how many atoms were actually involved** 2 2

5. Rules for balancing:
Assemble the _________ _________for all the reactants and products, using “+” and “→”
Count the number of atoms of each type appearing on both sides
Balance the elements one at a time by adding coefficients (the numbers in front) where you need more - __________
(hint: I prefer to save O until the very last)
_____________________to make sure it is balanced by counting the atoms on both sides.

6. Never
_________ change a subscript to balance an equation (You can only change coefficients)
If you change the subscript (formula) you are describing a different chemical.
H2O is a different compound than H2O2
_________ put a coefficient in the middle of a formula; they must go only in the _________
_____ NaCl is okay, but Na______Cl is not.

7. Chemical Reactions Element Before After C 1 H 4 2 O 3 Element Before
In more complicated chemical reactions, we may want to use a chart to keep track of the number of each kind of atom,
CH4 + O2  CO2 + H2O
Now lets count the atoms,
To balance Hydrogen.
Try putting a 2 in front of the H2O
To balance Oxygen
Try putting a 2 in front of the oxygen
Element
Before
After C 1 H 4 2 O 3
Element
Before
After C 1 H 4 O 2 _ _
Element
Before
After C 1 H 4 O

8. Some more practice. N2 + H2  NH3 Pb(NO3)2 + KI  PbI2 + KNO3
If there is a polyatomic that sticks together than you can balance it as a whole.
Pb(NO3) KI  PbI2 + KNO3
NaHCO H2SO4  Na2SO H2O CO2 _ _ _ _ _ _ _

9. Practice Balancing Examples
_AgNO3 + _Cu ® _Cu(NO3)2 + _Ag
_Mg + _N2 ® _Mg3N2
_P + _O2 ® _P4O10
_Na + _H2O ® _H2 + _NaOH
_CH4 + _O2 ® _CO2 + _H2O