# How can I balance this chemical equation Pb(NO3)2 + K2CrO4 = PbCrO4 + KNO3?

May 15, 2014

In order to balance the equation for the double displacement reaction of Lead (II) Nitrate and Potassium Chromate to produce Lead (II) Chromate and Potassium Nitrate.

We begin with the base equation provided in the question.

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

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.

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

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 hope this was beneficial.
SMARTERTEACHER