Chemistry Reference
In-Depth Information
When we refer to a chemical equation as “balanced,” we mean that the
appropriate coefficients have been used to show the same number of at-
oms of each element on both the product and reactant sides of the arrow.
If you understand conservation of matter, then you would expect the num-
ber of atoms that appear on each side of the chemical equation to be the
same. In fact, we must have the same number of atoms of each of the ele-
ments, on each side of the chemical equation. To check to see if that is
true, you may want to perform what I will call an “atomic tally.” Tally up
the number of atoms of each element on each side of the equation, and
make sure that they are the same, as demonstrated in Figure 6-1a.
Can you see how we
came up with each of
the elemental totals
shown in Figure 6-1a?
Remember that the
subscript numbers act
as multipliers for the el-
ements that appear be-
fore them, as described
in Lesson 5-1. The coefficient numbers act as multipliers for each of the
elements in the compound, so, for example, 6CO
2
shows 6 carbon atoms
and 12 oxygen atoms.
For this lesson, it will be important for you to master the skill of the
atomic tally. You will need to be able to check if an equation is balanced
before you can learn how to balance them correctly. Let's try a couple of
examples where you can do an atomic tally, before you check the answers.
The first example that we will look at represents a chemical reaction that
you may conduct in chemistry, as it is a common process for generating
hydrogen gas in the lab.
Atomic Tally for the Process of Respiration
Reactants
Products
C
6
H
12
O
6
+ 6O
2
6H
2
O + 6CO
2
Elements
{
# of atoms
{
CHOCHO
628628
Figure 6-1a
Example 1
Do an atomic tally for the following equation and determine if it is
balanced.
Zn + H
2
SO
4
ZnSO
4
+ H
2
Try to do an atomic tally for Example 1 before checking your answer.
See if our answers match.
