Balancing Chemical Equations. CONSERVATION OF MATTER. Conservation of Matter : states that matter cannot be created or destroyed by a chemical change
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.
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.
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
EXAMPLE: 2Na + Cl22NaCl
2 atoms of sodium 2 atoms of chlorine 2 atoms of sodium and chlorine
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.
1 Zn 1_
1 H 2_
1 Cl 2_
1 Al 2_
1 Fe 1_
1 O 3_
2 Al 1_
3 SO4 1_
1 Ca 1_