1. Balancing Chemical Equations

2. What is a balanced equation?  A balanced equation has equal numbers of each type of atom on each side of the equation. H 2 O( l )  H 2 (g) + O 2 (g) 2H 2 O( l )  2H 2 (g) + O 2 (g) H = O =

3. Why do we have to balance?  LAW OF CONSERVATION OF MASS Antoine Laurent Lavoisier (1743-94)Antoine Laurent Lavoisier (1743-94) “Matter is neither created nor destroyed."“Matter is neither created nor destroyed."  You must have the same number of atoms on the left as on the right

4. H 2 + O 2  H 2 O

5. RULES! RULES! RULES! 1. You cannot change the subscript H 2 + O 2 ---> H 2 O 2 2. You cannot place a coefficient in the middle of the formula H 2 + O 2 ---> H 2 2O 3. Make sure that your final set of coefficients are all whole numbers with no common factors other than one. 4 H 2 + 2 O 2 ---> 4 H 2 O Hydrogen gas + oxygen gas yields water H 2 (g) + O 2 (g)  H 2 O

6. H 2 + O 2  H 2 O

7. Balance this equation: H 2 + Cl 2 ---> HCl Remember that the rule is: A balanced equation MUST have EQUAL numbers of EACH type of atom on BOTH sides of the arrow.

8. Balance this equation: O 2  O 3  Hint – find the least common multiple

9. MINOH CHEMISTRY  Helpful Hint  If you aren’t sure where to start balancing first, list your atoms in this order MetalsMetals IonsIons NonmetalsNonmetals OxygenOxygen HydrogenHydrogen

10. How many oxygens are indicated: 3 Ca(NO 3 ) 2

11. Zn + HCl ---> ZnCl 2 + H 2

12. KClO 3 ---> KCl + O 2

13. S 8 + F 2 ---> SF 6

14. Polyatomics Tricks  IF a polyatomic group appears as a both a reactant and a product, you can treat it like an element. Mg(NO 3 ) 2 + Ag  AgNO 3 + Mg Mg(NO 3 ) 2 + Ag  AgNO 3 + Mg _____Ag _____ _____Mg _____ _____NO 3 _____

15. Fractional Coefficients  Be careful on using fractions. For example, 1/2 H 2 O is not a correct use of fractions.  Why not? 1/2 H 2 = one H atom, but 1/2 O = one half of one atom. but 1/2 O = one half of one atom.  You cannot split atoms in chemical reactions.  Generally speaking, fractions are mostly used with diatomics (with O 2 is the most common)

16.  http://funbasedlearning.com/ chemistry/chembalancer/defa ult.htm