1. Unit 3: Balancing Equations
Section 2: Balancing Techniques

2. Counting Atoms
To balance equations, you must be able to count the atoms given
Subscripts
Parentheses
Coefficients

3. Subscripts
Small-sized numbers that are written after the element symbol and placed slightly lower
H2O
2- H atoms
1- O atom
NH4NO3
2- N atoms
4- H atoms
3- O atoms

4. Parentheses Used to group elements together Ca(NO3)2 Mg3(PO4)2
1- Ca atom
2- N atoms
6- O atoms
Mg3(PO4)2
3- Mg atoms
2- P atoms
8- O atoms

5. Coefficients
Number placed in front of the formula, to multiply the entire formula
3Ca(NO3)2
3- Ca atoms
6- N atoms
18- O atoms
5Mg(C2H3O2)2
5- Mg atoms
20- C atoms
30- H atoms
20- O atoms

6. Practice Time
Answer questions 1-6!

7. Balanced Equation A chemist’s recipe
Tells what reactants and its amount to mix together
Tells what the end product(s) and its amount will be

8. Balancing Rules Can only add coefficients to balance, not subscripts
Never try to balance the number of oxygen atoms first, start with another element
Coefficients must be whole numbers

9. Balancing Unbalanced equation: Balanced equation: CH4 + O2  CO2 + H2O
C C-1
H H-2
O O-3
Balanced equation:
CH4 + 2O2  CO2 + 2H2O

10. Balancing Unbalanced equation: Balanced equation: Al2O3  Al + O2
Al Al-1
O O-2
Balanced equation:
2Al2O3  4Al O2

11. Work on the practice problems!
Practice Time
Work on the practice problems!