Balancing Chemical Equations

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# Balancing Chemical Equations - PowerPoint PPT Presentation

Balancing Chemical Equations. CONSERVATION OF MATTER. Conservation of Matter : states that matter cannot be created or destroyed by a chemical change

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### Balancing Chemical Equations

CONSERVATION OF MATTER

Conservation of Matter: states that matter cannot be created or destroyed by a chemical change

EXAMPLE: When a log burns, the wood disappears and ashes are left. Although the ashes seem much smaller than the wooden log, the log has the same mass as the ashes. As the log burns, in addition to the ashes, water and carbon dioxide are produced. If you could find the mass of these products and add them together, you would find that they equal the mass of the original log.

BALANCING CHEMCIAL EQUATIONS

The amount of matter present in the products must always

equal the amount of matter present in the reactants. A

chemical equation shows the atoms and molecules that are

involved in the reaction. When the number of atoms of each

element is the same on both sides of the equation, the equation is

said to be balanced.

EXAMPLE: Na + Cl2 NaCl

1 atom of sodium 2 atoms of chlorine 1 atom of sodium and chlorine

This is not a balanced equation because the number of

atoms for each element on both sides of the arrow are not equal.

Coeffiecients

A coefficient has to be added in front of Na on the

reactants side of the reaction and the NaCl on the

products side of the reaction to balance the

equation.

EXAMPLE: 2Na + Cl22NaCl

2 atoms of sodium 2 atoms of chlorine 2 atoms of sodium and chlorine

TO BALANCE A CHEMICAL EQUATION:

1. Write a formula equation with correct symbols and formulas.

2. Count the number of atoms of each element on each side of the arrow.

3. Balance atoms by using coefficients. (A coefficient, or whole number, is written before the formulas for reactants and products. The number shows how many molecules of a substance are involved in a chemical reaction.)

4. Check your work by counting atoms of each element.

N2(g) + 3H2(g)  2NH3(g)

__2___N__1_2__

6_2___H__3_6__

Zn + HCl  ZnCl2 + H2

1 Zn 1_

1 H 2_

1 Cl 2_

Al + FeO  Al2O3 + Fe

1 Al 2_

1 Fe 1_

1 O 3_

Al2(SO4)3 + Ca(OH)2 Al(OH)3 +CaSO4

2 Al 1_

3 SO4 1_

1 Ca 1_

2_OH 3_