Balancing Equations November , 2.009 *10 3

Balancing EquationsNovember , 2.009 *103 Objective:

SWBAT apply law of conservation of mass to chemical reactions by balancing!

Catalyst: Name the reactants in this equation.

Fe + AlOH3 FeOH2 _+ Al Name the products in this equation.

2H2 + O2 2H2O

121

Agenda

Catalyst Go over test! Balancing Equations Practice Exit Question

Whiteboard Practice

How many atoms are in these compounds?

AlCl3 H2O H2O2

KCl Be3S2

Balancing equations RULES!

Key Point #1: When balancing equations, Never, Never, NEVER change subscripts, only coefficients!

Yo, Mr. Jhaveri

What is a coefficient?

GOOD QUESTION!

Coefficient

A coefficient is a whole number comes in front of the compound, never in the middle!

You multiply the coefficient to all the numbers in the compound

2AlCl3

Do you get it?

3AlCl3

How many atoms of each element do they have?

3 Aluminum’s 9 Chlorine’s

Whiteboard Practice

2AlCl3 4H2O 6H2O2

5KCl 2Be3S2

Why is the top equation wrong? (5 minutes) – 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 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

Worksheet!

Exit Question

Balance the following equations:

KClO3 ---> KCl + O2

S8 + O2 ---> SO3