1. Chemical equation the symbolic representation of a chemical reaction (process) wherein the
reactant entities are on left side and change into
product entities on right-hand side

2. Chemical Equation Symbols
The arrow  can be read as “yields” or “produces”
The + sign reads as “and” or “plus”

3. Chemical Equation Symbols
The arrow  can be read as “yields” or “produces”
Coefficients are the numbers in front of the formulas
Coefficients can be changed to balance chemical equations
Subscripts tell us how many atoms or molecules we have
NEVER change subscripts when balancing chem. equations

4. Balancing Equations like solving a puzzle
Br2 + Al  Al2Br6 (not balanced)
Balance using coefficients

5. Balancing Equations
Reactants  Products
O2 + H2  H2O

6. Balancing Equations Reactants  Products
O2 + H2  H2O but this equation is not balanced
why not?

7. Balancing Equations
Conservation of Mass- Mass and/or Atoms are not Created or Destroyed during a chemical reaction. There must be the Same number of atoms on each side of the equation to balance the chemical equation.

8. Steps to Balance Chemical Equations
1. Write unbalanced equation.
2. Count # atoms on each side.
3. Add coefficients to make #s of atoms equal.
Coefficient  subscript = # of atoms
4. If necessary reduce coefficients to lowest possible ratio (never change subscripts)
Update and Double check atom balance!!!

9. Balancing Equations
Step 1. Write unbalanced equation
O2 + H2  H2O

10. Balancing Equations Step 2. Count # of atoms on each side
O2 + H2  H2O
O = = 1
H = H = 2

11. Balancing Equations
3. Add coefficients to make # of atoms = on each side
O2 + H2  H2O
O = = 1
H = H = 2

12. Balancing Equations
3. Add coefficients to make # of atoms = on each side
O H2  2 H2O
O = = 2
H = H = 4

13. Balancing Equations
4. If necessary find lowest ratio (never change subscripts)
O H2  2 H2O
O = = 2
H = H = 4

14. Balancing Equations 5. Update and double check work O2 + 2 H2  2 H2O

15. Balancing Steps Al + CuCl2  Cu + AlCl3
1. Write the unbalanced equation.
Al CuCl2  Cu AlCl3

16. Balancing Steps 1 Al 1 1 Cu 1 2 Cl 3 1. Write the unbalanced equation.
2. Count atoms on each side.
Al CuCl2  Cu AlCl3 Al
1 Cu Cl

17. Coefficient  subscript = # of atoms
Balancing Steps
1. Write the unbalanced equation.
2. Count atoms on each side.
3. Add coefficients to make #s equal.
Coefficient  subscript = # of atoms
Al CuCl2  Cu AlCl3 Al
1 Cu Cl

18. Coefficient  subscript = # of atoms
Balancing Steps
1. Write the unbalanced equation.
2. Count atoms on each side.
3. Add coefficients to make #s equal.
Coefficient  subscript = # of atoms
Al CuCl2  Cu AlCl3 Al
3 Cu Cl

19. Coefficient  subscript = # of atoms
Balancing Steps
1. Write the unbalanced equation.
2. Count atoms on each side.
3. Add coefficients to make #s equal.
Coefficient  subscript = # of atoms
2 Al CuCl2  3 Cu AlCl3 Al
3 Cu Cl

20. Coefficient  subscript = # of atoms
Balancing Steps
1. Write the unbalanced equation.
2. Count atoms on each side.
3. Add coefficients to make #s equal.
Coefficient  subscript = # of atoms
4. Reduce coefficients to lowest possible ratio, if necessary.
5. Double check atom balance!!!

21. Helpful Tips
Balance one element at a time. Balance most complicated compound first!
Update ALL atom counts after adding a coefficient.
Balance (polyatomic ions) as (single units).
“1 SO4” instead of “1 S” and “4 O”
Balance most complicated compound first, balance oxygen and hydrogen last (MINOH metals, ions, non-metals, oxygen, hydrogen)
Ask yourself this question what am I forced to do to balance the equation???

22. Examples
____ Mg ____ O2  ____ MgO

23. Examples
2 Mg O2  2 MgO

24. Examples
____ Al ____ S  ____ Al2S3

25. Examples
2 Al S  Al2S3
____ C3H8 +____ O2  ____ CO2 + ____ H2O

26. Examples
2 Al S  Al2S3
C3H8 + 5 O2  3 CO2 + 4 H2O

27. More Examples
___ Al +____ H2SO4  ____Al2(SO4)3 +____ H2

28. More Examples
2 Al + 3 H2SO4  Al2(SO4) H2

29. Helpful Tips Balance one element at a time.
Update ALL atom counts after adding a coefficient.
Balance (polyatomic ions) as (single units).
“1 SO4” instead of “1 S” and “4 O”
Balance most complicated compound first, balance oxygen and hydrogen last
Ask yourself this question what am I forced to do to balance the equation???