# How do you balance chemical equations step by step?

Dec 8, 2014

Let us use a double displacement reaction of Lead (II) Nitrate and Potassium Chromate to produce Lead (II) Chromate and Potassium Nitrate to practice balancing an equation.

We begin with the base equation provided in the question.

$P b {\left(N {O}_{3}\right)}_{2 \left(a q\right)} + {K}_{2} C r {O}_{4 \left(a q\right)} \rightarrow P b C r {O}_{4 \left(s\right)} + K N {O}_{3 \left(a q\right)}$

Looking at the the atom inventory

Reactants
$P b = 1$
$N {O}_{3} = 2$
$K = 2$
$C r {O}_{4} = 1$

Products
$P b = 1$
$N {O}_{3} = 1$
$K = 1$
$C r {O}_{4} = 1$

We can see that the $K$ and $N {O}_{3}$ are imbalanced.

If we add a coefficient of 2 in front of the $K N {O}_{3}$ this will balance the equation.

$P b {\left(N {O}_{3}\right)}_{2 \left(a q\right)} + {K}_{2} C r {O}_{4 \left(a q\right)} \rightarrow P b C r {O}_{4 \left(s\right)} + 2 K N {O}_{3 \left(a q\right)}$

Note that I leave the polyatomic ions$N {O}_{3}$ and $C r {O}_{4}$ together when they appear on both sides of the equation seeing them as one unit not separate elements.

I would watch the following videos to understand the process of balancing equations more in depth.