General Chemistry
Zumdahl Chapter 7 Notes
Chemical Reactions
Week of 1/26/15, Expected test date, Tuesday 2/3/15
Standard: HS-PS1-7 Use mathematical
representations to support the claim that
atoms, and therefore mass, are
conserved during a chemical reaction.
Introduction

Where do we see chemical reactions?(1)
Everywhere! Cars driving, hair growing,
clothes being made, etc…
7.1 Evidence for a Chemical
Reaction p. 193 of book
Most chemical reactions give a visual
signal when they occur.
 What are some examples of these visual
changes?(2)

◦
◦
◦
◦
Color change
Precipitate (solid) forms
Gas is formed (bubbles)
A flame forms
7.2 Chemical Equations, p. 195

Define
◦ Chemical reaction(3): Atoms of different
compounds are rearranged forming new
compounds
◦ Chemical equation(4): A visual representation
of a chemical reaction
◦ Reactant(5): Chemicals before the reaction
◦ Products(6): Chemicals after the reaction
7.2 Chemical Equations

What are the abbreviations for
◦
◦
◦
◦
Solid (7): (s)
Liquid (8): (l)
Gas (9): (g)
Dissolved in water or aqueous (10): (aq)
7.3 Balancing Chemical Equations,
p. 200

It is important to understand that in a
chemical reaction atoms are neither
created nor destroyed.
◦ There are the same amount of each atom on
the reactant side as there are on the product
side.
7.3 Balancing Chemical Equations

The burning of methane gas produces
carbon dioxide and water
CH4(g) + O2(g)  CO2(g) + H2O(l)
What is wrong with this?(11)
Not balanced!
CH4(g) + 2O2(g)  CO2(g) + 2H2O(l)
7.3 Balancing Chemical Equations
The chemical formation of water
 H2(g) + O2(g)  H2O(l)
 What is wrong with this?(12) Not
balanced
2H2(g) + O2(g)  2 H2O(l)
 Define coefficient(13): The number of
compounds that is needed to make
equation balanced.

7.3 Balancing Chemical Equations
Balance (14)
C2H5OH(l) + O2(g)  CO2(g) + H2O(l)
C2H5OH(l) + 3O2(g)  2CO2(g) + 3H2O(l)

N2(g)+H2(g) NH3(g)
N2(g)+3H2(g)2 NH3(g)
O2(g)  O3(g)
3O2(g)  2O3(g)