Let's look at a third example:

HCl + Ca(OH)₂ → H₂O + CaCl₂

In this reaction we cannot count the ions (hydroxide) because there is no hydroxide on the right side. Therefore we will have to deal with each element separately.

Left Side	Right Side
H = 3	H = 2
Cl = 1	Cl = 2
Ca = 1	Ca = 1
O = 2	O = 1

The Ca's are balanced, but nothing else is. Although it is tempting to start with the H's (since they appear first) it will be easier to NOT do this because the H's appear in BOTH of the compounds on the left side. This means that there are two different ways that the number of hydrogen atoms can be changed.

Instead, let's skip the H's and move on to the Cl's. There is 1 Cl atom on the left and 2 on the right. So, we'll add a coefficient of 2 on the left side and then recount:

2 HCl + Ca(OH)₂ → H₂O + CaCl₂

Left Side	Right Side
H = 4	H = 2
Cl = 2	Cl = 2
Ca = 1	Ca = 1
O = 2	O = 1

Now, the calcium and chlorine are both balanced. Still avoiding the hydrogen, we can look at the oxygen (2 on the left and one on the right). Adding a coefficient of 2 on the right side (for the water) gives:

2 HCl + Ca(OH)₂ → 2 H₂O + CaCl₂

Left Side	Right Side
H = 4	H = 4
Cl = 2	Cl = 2
Ca = 1	Ca = 1
O = 2	O = 2

Everything is balanced.

So, a general rule:

It is possible to start balancing by looking at any element or ion in the reaction, but if an element appears in more than one place on the same side, it may be worth avoiding.

One last example: