CH4 (g) + O2 (g) ® CO2 (g) + 2H2O(g)
2. Balance others leaving the
element that occurs by itself last.
–In this example C or H, depending on which you started
with, and then finally oxygen.
–Since we started with C and then moved on to H, we have
only O to balance.
–There are 2 O atoms on the left but 4 O atoms on the
right, and just as with H, we can multiply O2 by 2 to
raise the number of O atoms on the left to 4.
CH4 + 2O2 ® CO2 + 2H2O
–Notice balancing the element (here O2) that occurs by
itselft last does not change the number of other already-balanced
atoms in the reaction.