Name:____________________________________________ Date:______________ Period:_______
Balancing Chemical Equations
According to the law of conservation of mass, matter cannot be created or destroyed. So… in a
chemical reaction atoms cannot be created or destroyed – if there are 4 atoms of nitrogen on the
reactants side of an equation, there must be 4 atoms of nitrogen on the products side.
Example:
Pb(NO3)4 +
CaSO4 --->
Pb(SO4)2 +
Ca(NO3)2
Examine the above chemical equation. Is the nitrogen balanced?_______ If not, how many atoms
of nitrogen are on the reactants side of the equation?_______ How many atoms of nitrogen are
produced?_______ How can the nitrogen atoms be balanced, or equal, on both sides of the
equation?___________________________________ By placing a coefficient of 2 in front of the calcium
nitrate product.
___Pb(NO3)4 + ___ CaSO4 ---> ___ Pb(SO4)2 + 2 Ca(NO3)2
One method of balancing is balancing by inspection – also known as trial and error. Most
textbooks and many teachers teach this method. It is effective, though may lead to frustration
when trying to balance certain types of chemical equations. To balance by trial and error, pick
one element on the product side and balance it; then, choose another element and balance;
repeat for each and every element present. The last step is to go back and re-check each element
to verify that each is still balanced. If they are not balanced, continue the process… (hence the
name: trial and error). To balance the entire reaction above you need coefficients of 1, 2, 1, 2 –
reading left to right.
_1_Pb(NO3)4 + _2_ CaSO4 ---> _1_ Pb(SO4)2 + 2 Ca(NO3)2
THE AMAZING SEVEN STEP METHOD!!!
1. Check for diatomic molecules (these exist only in nature bonded together – they do not
exist as a single atom). You need to learn these 7 diatomics!!!

They are: H2, N2, O2, F2, Cl2, Br2, and I2

If these elements are present in a reaction, they must have a subscript of 2

Fe + O ---> Fe2O3 must be changed to Fe + O2 ---> Fe2O3
2. Balance the metal atoms present
3. Balance the nonmetal atoms present
4. Balance oxygen (if it is present as O2)
5. Balance hydrogen (if it is present as H2)
6. Recount all atoms to check if they are balanced
7. If the coefficients can be reduced to simpler whole numbers reduce them. For example, if
you have coefficients of 4, 2, 4, 4 – reduce them to 2, 1, 2, 2. If the coefficients are 4, 3, 4, 4
– they cannot be reduced