Balancing chemical equations by inspection
Consider the reaction of methane (CH4) with oxygen to give carbon dioxide and water.
Step 1:
The equation must use correct formulae and have the form reactants
products.
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.
No change required above. C is balanced
Step 3: Then balance the one of the remaining atoms that occurs least often.
Step 3: Continue by balancing any remaining atoms.
Step 1:
The equation must use correct formulae and have the form reactants
products.CH4 + O2 CO2 + H2O
Step 2: CO2 + H2OCount the numbers of each type of atom in reactants in products.
1 C 4 H and 2 O (reactants) 1 C 2 H 3 O (products)
1 C 2 H 3 O (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.
No change required above. C is balanced
Step 3: Then balance the one of the remaining atoms that occurs least often.
H is chosen because it is in one reactant and one product.
CH4 + O2 CO2 + 2H2O
CH4 + O2
CO2 + 2H2O1 C and 4 H and 2 O 1 C and 4 H and 4 O
1 C and 4 H and 4 OStep 3: Continue by balancing any remaining atoms.
CH4 + 2O2 CO2 + 2H2O
CO2 + 2H2O1 C and 4 H and 4 O 1 C and 4 H and 4 O
1 C and 4 H and 4 O