Balanced Chemical Equations

C OO

C O C OOO CO

The Law of Conservation of Mass:

In any chemical reaction matter cannot be created or destroyed.

We call this equation unbalanced because the atoms are not conserved.

H2 (g) + O2 (g) H2O (g)

HOH

HH

O

2 2

HH

O

HH

O

Balancing Rules:

1. You cannot change a formula. (what it is)

H2O3 3

2. You can ONLY add a coefficient. (how many there are)

2 a. Coefficients can only be placed in front.

You can write 2 H2O, but not H22O.

2 b. Coefficients apply to the whole molecule.

H2O3

BALANCING STEPS:

1. Determine the number of atoms for each element in reactants and products.

2. Balance metals first, then non-metals.

3. Balance single elements last.

4. Check and recount all the atoms.

Use trial and Error.

C + O2 CO2

C: 1 C: 1 O: 2 O: 2

BALANCED

HCl + MgBr2 MgCl2 + HBr

H: 1 H: 1 Cl: 1 Cl: 2 Mg: 1 Mg: 1 Br: 2 Br: 1

BALANCED

2

(2) = 2

(2) = 2

2

(2) = 2(2) = 2

CH4 + O2 CO2 + H2OC: 1 C: 1 H: 4 H: 2 O: 2 O: 2 + 1

BALANCED

2

(2) = 4(2) = 4

2

(2) = 4

K(NO3) + Mg Mg(NO3)2 + K

K: 1 K: 1 NO3: 1 NO3: 2 Mg: 1 Mg: 1

BALANCED

2

(2) = 2(2) = 2

2

(2) = 2

BalancingWord Equations

Step 1: Write reactant and products using the symbols + and

Step 2: Write correct formula for reactant and product (skeleton equation)

Step 3: Next we have to balance the equation

Step 4: Complete the equation by adding all states(solid, liquid, gas)

Solid aluminum and nitrogen gas react to produce solid aluminum nitride.

aluminum nitrogen aluminum nitride

Al + N AlN(s) (g) (s)22 2

++3 -3

Solid potassium iodide and chlorine gas react to produce potassium chloride and liquid iodine.

potassium iodide

chlorine potassiumchloride

KI + Cl KCl + I (s) (g) (l)22 2

++1 -1

iodine++1 -1

2

Methane gas and oxygen gas react to produce carbon dioxide gas and water.

methane oxygen carbondioxide

CH4 + O CO2 + H2O (g) (g) (l)2 22

+ water+

(g)

· explain the Law of Conservation of Mass

· differentiate between subscripts and coefficients

· balance skeleton equations by adding coefficients

· translate word equations into balanced chemical reactions

· translate balanced chemical reactions into word equations