Consider the reaction of heptane (C7H16) with oxygen to give carbon dioxide and water.
Step 1:
The equation must use correct formulae and have the form reactants
products.
C7H16 + O2 CO2 + H2O
Step 2:
Count the numbers of each type of atom in reactants in products.
Step 3: Balance the element that occurs in the fewest formulae by changing the coefficient in one or more of these.
If there is more than one element in this category, choose an element other than oxygen or hydrogen.
C7H16 + O2 7CO2 + H2O
Step 4: Then balance the one of the other atoms that occurs least often.
Step 5: Continue by balancing any remaining atoms.
Step 1:
The equation must use correct formulae and have the form reactants
products.C7H16 + O2
CO2 + H2OCount the numbers of each type of atom in reactants in products.
7 C 16 H and 2 O in reactants 1 C 2 H 3 O in products
1 C 2 H 3 O in productsStep 3: Balance the element that occurs in the fewest formulae by changing the coefficient in one or more of these.
If there is more than one element in this category, choose an element other than oxygen or hydrogen.
C7H16 + O2
7CO2 + H2OStep 4: Then balance the one of the other atoms that occurs least often.
H is chosen because it is in one reactant and one product.
C7H16 + O2 7CO2 + 8H2O
C7H16 + O2
7CO2 + 8H2O7 C and 16 H and 2 O 7 C and 16 H and (14+8) O
7 C and 16 H and (14+8) OStep 5: Continue by balancing any remaining atoms.
C7H16 + 11O2 7CO2 + 8H2O
7CO2 + 8H2O7 C and 16 H and 22 O7 C and 16 H and (14+8) O
7 C and 16 H and (14+8) O