Transcript Balancing Chemical Reactions H 2 + O 2 H 2 O - stroh

November 121 , 2.009 x 103
1.
2.
NAME the reactants in this
equation.
 Fe + Al(OH)3  Fe(OH)2 + Al
NAME the products in this equation.

2 H2 + O2  2 H2O
Today’s Agenda
Catalyst
 Unit 4 Tracking and Test Review
 Begin Balancing Equations
 Practice Time
 Exit Question

Today’s Objectives
SWBAT track their Unit 4 mastery.
 SWBAT apply law of conservation
of mass to chemical reactions by
balancing!

Practice!

How many atoms are in each of these compounds?
AlCl3
 H 2O
 H 2O 2
 KCl
 Be3S2

Balancing equations RULES!
Key Point #1: When balancing
equations, Never, Never,
NEVER change subscripts, only
coefficients!
Yo, Ms. Stroh

What is a coefficient?

GOOD QUESTION!
Coefficient


A coefficient is a whole number
that comes in front of the
compound, never in the middle!
You multiply the coefficient to all the numbers
in the compound
2 AlCl3
Do you get it?
3 AlCl3

How many atoms of each element do
they have?
3 Aluminum atoms
 9 Chlorine atoms

Whiteboard Practice

Count the number of atoms of each element…
2 AlCl3
4 H2O
6 H2 O 2
5 KCl
2 Be3S2
Why is the top equation wrong?
You figure it out!

We never want to leave an equation written like
this…
H2 +

O2  H2O
We want to have it like this…
2H2 +
O2  2H2O
WHY???
L-C-M!!!
Key Point #2: Chemical reactions
MUST follow the law of
conservation of matter/mass.
 What
was that LCM again?
 If 3 carbons are in the reactants of a reaction,
then there darn well better be 3 carbons in the
products of a reaction.
Balancing Chemical Reactions
H2 + O2  H2O
__H__
__O__
Write down elements.
Balancing Chemical Reactions
H2 + O2  H2O
__H__
__O__
How many are there?
Balancing Chemical Reactions
H2 + O2  H2O
_2_H_2_
__O__
How many are there?
Balancing Chemical Reactions
H2 + O2  H2O
_2_H_2_
_2_O_1_
How many are there?
Balancing Chemical Reactions
Try These:
N2 + H2  NH3
P4O10 + H2O  H3PO4
Ca3P2 + H2O 
Ca(OH)2 + PH3
Balancing Chemical Reactions
Try These:
N2 + 3H2  2NH3
P4O10 + H2O  H3PO4
Ca3P2 + H2O 
Ca(OH)2 + PH3
Balancing Chemical Reactions
Try These:
N2 + 3H2  2NH3
P4O10 + 6H2O  4H3PO4
Ca3P2 + H2O 
Ca(OH)2 + PH3
Balancing Chemical Reactions
Try These:
N2 + 3H2  2NH3
P4O10 + 6H2O  4H3PO4
Ca3P2 + 6H2O 
3Ca(OH)2 + 2PH3
Independent Practice

Please complete the worksheet!
Exit Question

Balance the following equations:

KClO3  KCl
S + O2  SO3
 8
+ O2