NOTES Out 5 Balancing Equations.doc

(1)

Outcome 4 -- Balancing Equations

for Chemical Reactions

A) All reactions (chemical, physical or nuclear) follow the Law of Conservation of Mass which states that the mass at the beginning of the reaction must equal the mass at the end OR

the number of atoms on the REACTANT side must equal the number of atoms on the PRODUCT side.

B) Chemical Symbols represent elements. (Ex:

Na or K

)

C) Chemical Formulas are short-hand ways of representing compounds. (Ex:

K

2

O or NaCl

)

D) Chemical Reactions involve the interaction of two or more forms of matter (elements and/or compounds) in which the atoms are rearranged (because electrons are transferred or shared).

E) Chemical Equations are short-hand ways of representing a complete Chemical Reaction. (Ex:

2H

2

+ O

2



2H

2

O

)

Some WORDS & some HINTS

Subscripts … the 2 in K2O is a subscript …. A compound’s subscripts can NOT be modified.

Coefficient …. the 3 in 3NaCl is a coefficient . . . . these can be modified.

STEP TO BALANCING

EQUATIONS

Example Chemical Equation to be balanced Na + O2 Na2O

1) Determine the total number of atoms of EACH element on the Reactant Side of the equation.

Na + O2 Na2O

2) Find the total number of atoms of each element on the Product Side.

Na + O2  Na2O

3) If the numbers of atoms of each element are NOT equal, place Coefficients where needed.

Na + O2  Na2O

4) After adding Coefficients, Repeat steps 1 through 4 until you’ve BALANCED THE EQUATION.

Reactant

(2)

(3)

Outcome 4

–

Balancing Equations

for

Chemical Reactions

A) All reactions

(chemical,

physical or nuclear) follow the

Law of

Conservation of

Mass

which states that the

mass at the

beginning of

(4)

the number of

atoms

on the REACTANT side

must equal the number

of

atoms

on the

(5)

(6)

that the mass at the beginning of the reaction must equal the mass at the endOR the number of atoms on the REACTANT side must equal the number of atoms on the PRODUCT side.

Na or K

)

C) Chemical Formulas

are

short-hand ways of representing

(7)

Na or K

)

K

2

O or NaCl

)

D) Chemical

Reactions

involve

the interaction of two or more forms

of matter (elements and/or

(8)

E)

Chemical Equations

are

short-hand ways of representing a complete

Chemical Reaction

.

(9)

2H

2

+ O

2



2H

2

O

)

Some REMINDERS…

Subscripts

… the 2 in K2O is a

subscript ….

A compound’s

subscripts can NOT be

modified

.

(10)

STEP TO BALANCING

EQUATIONS

1) Determine the total number of

atoms of EACH

EACH

element on the

Reactant Side

and

Product

Side

of the equation.

Na + O

2 

Na

2 O

2) If the numbers of atoms of each element

are

NOT

equal, place

Coefficients

where

needed.

Reactant

Product

(11)

Na + O

2



Na

2

O

3) After adding Coefficients, Repeat

steps 1 and 2 until you’ve

BALANCED THE EQUATION.

TRY SOME:

Ca + S ---> CaS FeS2 + O2 ---> Fe2O3 + SO2

(12)

Ca + S ---> CaS

FeS2 + O2 ---> Fe2O3 + SO2

K + Cl2 ---> KCl

(13)

Outcome 4 -- Balancing Equations

for Chemical Reactions

Na or K

)

K

2

O or NaCl

)

2H

2

+ O

2



2H

2

O

)

STEP TO BALANCING

EQUATIONS

Na + O2 Na2O

Na + O2  Na2O

Reactant

(14)

Outcome 4 -- Balancing Equations

for Chemical Reactions

Na or K

)

K

2

O or NaCl

)

2H

2

+ O

2



2H

2

O

)

STEP TO BALANCING

EQUATIONS

Na + O2 Na2O

Na + O2  Na2O

Reactant

(15)

Outcome 4 -- Balancing Equations

for Chemical Reactions

Na or K

)

K

2

O or NaCl

)

2H

2

+ O

2



2H

2

O

)

STEP TO BALANCING

EQUATIONS

Na + O2 Na2O

Na + O2  Na2O

Reactant

(16)

Na + O2  Na2O

Outcome 4 -- Balancing Equations

for Chemical Reactions

Na or K

)

K

2

O or NaCl

)

2H

2

+ O

2



2H

2

O

)

STEP TO BALANCING

EQUATIONS

Na + O2 Na2O

Na + O2  Na2O

Reactant

(17)

Na + O2  Na2O

Outcome 4 -- Balancing Equations

for Chemical Reactions

Na or K

)

K

2

O or NaCl

)

2H

2

+ O

2



2H

2

O

)

STEP TO BALANCING

EQUATIONS

Na + O2 Na2O

Reactant

(18)

Na + O2  Na2O

Outcome 4 -- Balancing Equations

for Chemical Reactions

Na or K

)

K

2

O or NaCl

)

2H

2

+ O

2



2H

2

O

)

STEP TO BALANCING

EQUATIONS

Na + O2 Na2O

(19)

Na + O2  Na2O

Outcome 4 -- Balancing Equations

for Chemical Reactions

Na or K

)

K

2

O or NaCl

)

2H

2

+ O

2



2H

2

O

)

STEP TO BALANCING

EQUATIONS

Na + O2 Na2O

Product Side

(20)

Na + O2  Na2O

Outcome 4 -- Balancing Equations

for Chemical Reactions

Na or K

)

K

2

O or NaCl

)

2H

2

+ O

2



2H

2

O

)

STEP TO BALANCING

EQUATIONS

Product Side

(21)

Na + O2 Na2O

Na + O2  Na2O

Outcome 4 -- Balancing Equations

for Chemical Reactions

Na or K

)

K

2

O or NaCl

)

2H

2

+ O

2



2H

2

O

)

STEP TO BALANCING

EQUATIONS

(22)

Na + O2 Na2O

Na + O2  Na2O

Reactant