Download Balancing Chemical Equations

Balancing Chemical Equations
(Taken from Malone, Basic Concepts of Chemistry, 7th Edition.)
1. In general, it is easiest to consider balancing elements other than hydrogen (H)
and oxygen (O) first. Start with a compound on either side of the arrow that
contains the most atoms of elements other than H and O. Balance this element
first.
2. Balance all other atoms in the reaction except H and O.
3. Balance H and O next. Choose the one (H or O) that is present in the fewest
number of compounds and start with that one. For example, if H is present in
three compounds in the equation, and O present in two, start with O. In practice,
H is usually in the fewest compounds. After done with this element, do the other.
4. Finally, check to see that the atoms of all elements are balanced. This final
double check will reveal a lot of simple errors. If a fraction is used as one of the
coefficients in the balanced equation, multiply all coefficients by the denominator
of the fraction to obtain simple whole numbers.
Example 7-3 in text:
B2H6 + H2O → H3BO3 + H2
Using rule 1, ignore H and O, leaving B. There are 2 Bs in the first cpd on the left.
We need two on the right.
B2H6 + H2O → 2H3BO3 + H2
Checking rule 2, there are no other elements. Rule 3 says we now look at H and O.
Four cpds have H and O is in only 2. We begin with O. There are 6 O atoms on the
right of the arrow, we need 6 O atoms on the left.
B2H6 + 6H2O → 2H3BO3 + H2
Rule 4 takes us to the final element, H. There are 18 H atoms on the left and 8 H
atoms on the right. We can add 10 more H atoms by changing the coefficient on H2.
B2H6 + 6H2O → 2H3BO3 + 6H2
As a final check, we have 2 B on left, 2 B on right.
18 H on left, 18 H on right.
6 O on left, 6 O on right. Do the victory dance!