1.1 What is Chemistry?

11.1. Chemical Equations http://www.ck12.org

2NH 4 NO 3 (s)→2N 2 (g)+4H 2 O(l)+O 2 (g)

We can confirm that this equation is balanced by writing the followingTable11.7.

TABLE11.7: 2NH

Reactants Products

N 4 4

H 8 8

O 6 6

Example 11.7

Lead(II) nitrate reacts with sodium chloride to form lead(II) chloride and sodium nitrate. Write the balanced
chemical equation for this process.

Answer:

Write the general expression.

Pb(NO 3 ) 2 +NaCl→PbCl 2 +NaNO 3

Balance.

TABLE11.8: Pb(NO

Reactants Products

Pb 1 1

NO 3 2 2

Na 2 2

Cl 2 2

By keeping the polyatomic nitrate ion intact as a single unit, balancing this equation becomes somewhat simpler.
This was done because the ion exists unchanged on both sides of the equation. Note that this is in contrast to the
previous example, in which the nitrate ion decomposed to form other substances.

Lesson Summary

• The composition of gunpowder gradually changed as alchemists and scientists experimented with ways to
  make it even more explosive.


• Chemical reactions are described using chemical equations.


• Stoichiometric coefficients are used in chemical equations to indicate the amounts of reactants and products.


• Because of the law of conservation of mass (matter can neither be created nor destroyed through chemical
  reactions), chemical equations must have equal amounts of each specific atom on both sides of the equation.