The following steps frequently yield a correctly balanced equation without too much difficulty:
Step 1. Write an unbalanced skeletal equation by writing chemical formulas for each of the reactants and products.
Step 2. If an element occurs in only one compound on both sides, balance it first.
Step 3. If an element occurs as a free element on either side, balance it last. Always balance it by changing the coefficient on the free element, not the compound on the other side.
Step 4. If a balance equation contains coefficient fractions, change them to whole numbers by multiplying the entire equation by the appropriate factor.
Step 5. Check to make certain the equation is balanced by finding the total number of each type of atom on both sides of the equation.
Octane (C8H18), a component of gasoline, reacts with oxygen gas to form carbon dioxide and water.
CRITICAL THINKING QUESTIONS
Apply Step 1 to the combustion reaction of octane, C8H18, above.
___________________________ ® ____________________________
Is this reaction balanced? Why or why not?
According to Steps 2 and 3, in what order will you balance the atoms?
Rewrite your equation with carbon and hydrogen balanced. (See Step 3.)
Double check that carbon and hydrogen are balanced. Indicate the number of each. Carbon: ____________ Hydrogen: ____________
How many oxygen atoms are on the right? How many O2 molecules contain that many atoms? (It may be a fraction!)
Rewrite your equation with oxygen balanced.
Apply Step 4 to your reaction.
Apply Step 5. Record the number of each atom appearing on both sides.
Carbon: __________ Oxygen: ___________ Hydrogen: __________