1. Balancing Equations Balancing, Writing, and Naming Equations

2. Balancing Equations 3. Balancing Equations

Law of Conservation of Matter:

• In a chemical reaction, matter can be neither created nor destroyed.

• In a chemical reaction, the amount of reactants equal the amount of products.

4. Balancing Equations

Paraphrase:

Law of Conservation ofAtoms :

• The number of atoms of each type of element must be the same on each side of the equation.

5. Balancing Equations

Hydrogen and oxygen are diatomic elements.

Their subscripts cannot be changed.

The subscripts on water cannot be changed.

Hydrogen + oxygenwater

H 2 +O 2 H 2 O

6. Balancing Equation

Count the atoms on each side.

• Reactant side: 2 atoms H and 2 atoms O

• Product side: 2 atoms H and 1 atom O

H 2+O 2 H 2 O

7. Balancing Equations

H 2+O 2 H 2 O

If the subscripts cannot be altered, how can the atoms be made equal?

Adjust the number of molecules by changing thecoefficients .

8. Balancing Equations

Reactants:2 atoms of H and 2 atoms of O

Products:4 atoms of H and 2 atoms of O

H is no longer balanced!

H 2 +O 2 2 H 2 O

9. Balancing Equations

Reactant side:4 atoms of H and 2 atoms of O

Product side:4 atoms of H and 2 atoms of O

Its Balanced!

2 H 2+ O 2 2 H 2 O

10. Balancing Equations

Count atoms.

• Reactants:2 atoms N and 2 atoms H

• Products:1 atom N and 3 atoms of NH 3

N 2 +H 2 NH 3

Nitrogen + hydrogenammonia

11. Balancing Equations

Nothing is balanced.

Balance the nitrogen first by placing a coefficient of 2 in front of the NH 3 .

N 2 +H 2 2 NH 3

12. Balancing Equations

Hydrogen is not balanced.

Place a 3 in front of H 2.

Reactant side:2 atoms N, 6 atoms H

Product side:2 atoms N, 6 atoms H

N 2 +3 H 2 2 NH 3

13. Balancing Equations

Count atoms.

Reactants:Ca 3 atoms, P 2 atoms, O 8 atoms; H atoms, S 1 atom, O 4 atoms

Ca 3 (PO 4 ) 2 +H 2 SO 4 CaSO 4 +H 3 PO 4

14. Balancing Equations

Side note on Ca 3 (PO 4 ) 2

The subscript after the phosphate indicates two phosphate groups.

This means two PO 4 3-groups with two P and eight O atoms.

15. Balancing Equations

Ca 3 (PO 4 ) 2 +H 2 SO 4 CaSO 4+H 3 PO 4

Count atoms in the product.

Ca atoms 1, S atom 1, O atoms 4; H atoms 3, P atom 1, O atoms - 4

16. Balancing Equations

In this equation, the ion groups do not break up.

Instead of counting individual atoms, ion groups may be counted.

Ca 3 (PO 4 ) 2 +H 2 SO 4 CaSO 4+H 3 PO 4

17. Balancing Equations

Ca 3 (PO 4 ) 2 +H 2 SO 4 CaSO 4+H 3 PO 4

Reactants:Ca 2+ 3, PO 4 3-- 2, H + 2, SO 4 2+- 1

Products:Ca 2+- 1, SO 4 2-- 1, H +- 3, PO 4 3-- 1

18. Balancing Equations

Balance the metal first by placing a coefficient of 3 in front of CaSO 4 .

Products:Ca 3 atoms,SO 4 2-- 3 groups

Ca 3 (PO 4 ) 2 +H 2 SO 4 3 CaSO 4+H 3 PO 4

19. Balancing Equations

Three sulfate groups are needed on the reactant side so place a coefficient of 3 in front of H 2 SO 4 .

3H 2 SO 4gives 6 H +and 3 SO 4 2- .

Neither phosphate nor calcium is balanced.

Ca 3 (PO 4 ) 2 +3 H 2 SO 4 3 CaSO 4+H 3 PO 4

20. Balancing Equations

A coefficient of 2 placed in front of H 3 PO 4which balances both hydrogen and phosphate.

Ca 3 (PO 4 ) 2 +3 H 2 SO 4 3 CaSO 4+2 H 3 PO 4

21. Balancing Equations

The sulfate group breaks up.Each atom must be counted individually.Ugh!

Reactants:Cu 1, H 2, S 1, O 4

Products:Cu 1, S 1, O - 4, H 2, O 1, S 1, O - 2

Cu+H 2 SO 4

CuSO 4+H 2 O+SO 2

22. Balancing Equations

Sulfur is not balanced.

Place a two in front of sulfuric acid.

Count atoms:2 H 2 SO 4 H 4, S 2, O - 8

Cu+2 H 2 SO 4

CuSO 4 +H 2 O+SO 2

23. Balancing Equations

Hydrogen needs to be balanced so place a 2 in front of the H 2 O.

Count the number of atoms.

Cu+2 H 2 SO 4

CuSO 4 +2 H 2 O+SO 2

24. Balancing Equations

Reactants:Cu 1, H 4, S 2, O 8

Products:Cu 1, S 1, O 4, H 4, O 2, S 1, O 2= Cu 1, S 2, H 4, O 8

Its balanced!

Cu+2 H 2 SO 4

CuSO 4 +2 H 2 O+SO 2

25. Balancing Equations

Balancing hints:

• Balance the metals first.

• Balance the ion groups next.

• Balance the other atoms.

• Save the non ion group oxygen and hydrogen until the end.

26. Balancing Equations

This method of balancing equations is the inspection method.

The method is trial and error.

Practice.